We have a string of letters 'a' and 'b'. We want to perform some operations on it. On each step we choose one of substrings "ab" in the string and replace it with the string "bba". If we have no "ab" as a substring, our job is done. Print the minimum number of steps we should perform to make our job done modulo 109 + 7.

The string "ab" appears as a substring if there is a letter 'b' right after the letter 'a' somewhere in the string.

Input

The first line contains the initial string consisting of letters 'a' and 'b' only with length from 1 to 106.

Output

Print the minimum number of steps modulo 109 + 7.

Examples

Input

ab


Output

1


Input

aab


Output

3

Note

The first example: "ab"  →  "bba".

The second example: "aab"  →  "abba"  →  "bbaba"  →  "bbbbaa".
			
			
			    				import java.io.*;
			    			import java.math.BigInteger;
			    			import java.util.*;
			    				
			    				
			    				public class Practice {
			    					private static InputStream stream;
			    					private static byte[] buf = new byte[1024];
			    					private static int curChar;
			    					private static int numChars;
			    					private static SpaceCharFilter filter;
			    					private static PrintWriter pw;
			    					private static long mod=1000000007;
			    				
			    				    public static void main(String[] args) {
			    				    	InputReader(System.in);
			    						pw = new PrintWriter(System.out); 
			    				        new Thread(null ,new Runnable(){
			    				           public void run(){
			    				               try{
			    				                   solve();//This is solution method
			    				                   pw.close();
			    				               } catch(Exception e){
			    				                   e.printStackTrace();
			    				               }
			    				           }
			    				       },"1",1<<26).start();
			    				   }
			    				    static long sort(int a[])
			        		    	{  int n=a.length;
			        		    		int b[]=new int[n];	
			        		    		return mergeSort(a,b,0,n-1);}
			        		    	static long mergeSort(int a[],int b[],long left,long right)
			        		    	{ long c=0;if(left<right)
			        		    	 {   long mid=left+(right-left)/2;
			        		    		 c= mergeSort(a,b,left,mid);
			        		    		 c+=mergeSort(a,b,mid+1,right);
			        		    		 c+=merge(a,b,left,mid+1,right); }	
			        		    		return c;	 }
			        		    	static long merge(int a[],int  b[],long left,long mid,long right)
			        		    	{long c=0;int i=(int)left;int j=(int)mid; int k=(int)left;
			        		    	while(i<=(int)mid-1&&j<=(int)right)
			        		    	{ if(a[i]>a[j]) {b[k++]=a[i++]; }
			        		    	else	{ b[k++]=a[j++];c+=mid-i;}}
			        		    	while (i <= (int)mid - 1)   b[k++] = a[i++]; 
			        		    	while (j <= (int)right) b[k++] = a[j++];
			        		    	for (i=(int)left; i <= (int)right; i++) 
			        		    		a[i] = b[i];  return c;  }
			        		    		    
			    				    
			    				    
			        		    	public static void solve() {
		
		
			        		    		HashSet<Integer> prime=new HashSet<Integer>();
			        		    		
			        		    	//	pw.println((int)Math.sqrt(5));
			        		    		String s=nextLine();
			        		    		long no_cons_b=0;
			        		    		long no_move=0;
			        		    		for(int i=s.length()-1;i>=0;i--){
			        		    			if(s.charAt(i)=='b')
			        		    		no_cons_b++;
			        		    			no_cons_b%=mod;
			        		    				if(s.charAt(i)=='b' && i>0 && s.charAt(i-1)=='a'){
			        		    		
			        		    				
			        		    				no_move+=no_cons_b;
			        		    				no_move%=mod;
			        		    				no_cons_b*=2;
			        		    				no_cons_b%=mod;
			        		    				i-=2;
			        		    				int flag=0;
			        		    				while(i>=0 && s.charAt(i)=='a'){
			        		    			//		pw.println(no_cons_b+"_____");
			        		    					no_move+=no_cons_b;
			        		    					no_cons_b*=2;
			        		    					no_cons_b%=mod;
			        		    					i--;
			        		    				no_move%=mod;
			        		    				}
			        		    				
			        		    				i++;
			        		    			}
			        		    			no_move%=mod;
			        		    			//pw.println(no_move);
			        		    		}
			        		    		pw.println(no_move);
			        		    		
			        		    		
			        		    	}
			        		    	static  long  PowerMod(long a, long b, long m) {
			        		    		   long  tempo;
			        		    		  if (b ==0 ){
			        		    		   tempo =  1;  //EXIT condition
			        		    		   }//if
			        		    		  else  if (b == 1) tempo = a;
			        		    		        else { long temp = PowerMod(a,b/2,m);
			        		    		            if (b%2 == 0)
			        		    		               tempo = (temp*temp)%m;
			        		    		            else
			        		    		     		    tempo = ((temp*temp)%m)*a%m;
			        		    				   }
			        		    		    return tempo;
			        		    		 }
			        		    	public static long trailingZeroes(long n) {
			        		    	    long count = 0;
		
			        		    	    while (n > 0) {
			        		    	        n /= 5;
			        		    	        count += n;
			        		    	    }
		
			        		    	    return count;
			        		    	}
			
			    				    public static int largestPrimeFactor(long number) {
			    				        int i;
		
			    				        for (i = 2; i <= number; i++) {
			    				            if (number % i == 0) {
			    				                number /= i;
			    				                i--;
			    				            }
			    				        }
		
			    				        return i;
			    				}
			    				   
			    					public static long pow(long n, long p) {
							    		if(p==0)
							    			return 1;
							    		if(p==1)
							    			return n;
							    		if(p%2==0){
							    			long temp=pow(n, p/2);
							    		return (temp*temp);
							    		}else{
							    			 	long temp=pow(n,p/2);
							    			 	temp=(temp*temp);
							    			 	return(temp*n);
							    			 	
							    		}
							    	}
			    				    public static String reverseString(String s) {
			    			    		StringBuilder sb = new StringBuilder(s);
			    			    		sb.reverse();
			    			    		return (sb.toString());
			    			    	}
			    				    private static BigInteger ncr(int n,int k){
			    				    	if (k < 0 || k > n) return BigInteger.ZERO;
			    				        if (n-k < k) k = n-k;
			    			
			    				        BigInteger x = BigInteger.ONE;
			    				        for (int i = 1; i <= k; i++) {
			    				            x = x.multiply(new BigInteger(""+(n-i+1)));
			    				            x = x.divide(new BigInteger(""+i));
			    				        }
			    			
			    				return x;
			    				    }
			    				    static long fact[];
			    				private static void factmod(int n,int mod){
			    					fact=new long[n+1];
			    					fact[0]=1;
			    					for(int i=1;i<=n;i++){
			    						fact[i]=i*fact[i-1];
			    						//fact[i]%=mod;
			    				
			    					}
			    					
			    				}
			    				private static long phi(long n){
			    					long ans=n;
			    					if(n%2==0)
			    						ans-=(ans/2);
			    					while(n%2==0)
			    					{
			    						n/=2;
			    						
			    					}
			    					for(int i=3;i*i<=n;i+=2){
			    						if(n%i==0){
			    						while(n%i==0){
			    							n/=i;
			    						}
			    						ans-=(ans/i);
			    						}
			    					}
			    					if(n>2)
			    						ans-=(ans/n);
			    					
			    					return ans;
			    				}
			    				static long d,x,y;
			    				static long modInverse(long A, long M)
			    				{
			    				extendedEuclid(A,M);
			    				return (x%M+M)%M;    //x may be negative
			    				}
			    				static void extendedEuclid(long A, long B) {
			    				if(B == 0) {
			    				d = A;
			    				x = 1;
			    				y = 0;
			    				}
			    				else {
			    				extendedEuclid(B, A%B);
			    				long temp = x;
			    				x = y;
			    				y = temp - (A/B)*y;
			    				}
			    				}
			    				static boolean prime[];
			    				static int spf[];
			    				public static void sieve(int n){
			    					prime=new boolean[n+1];
			    					spf=new int[n+1];
			    					
			    					Arrays.fill(spf, 1);
			    					Arrays.fill(prime, true);
			    				prime[1]=false;
			    					spf[2]=2;
			    					for(int i=4;i<=n;i+=2)
			    					{
			    						spf[i]=2;
			    						prime[i]=false;
			    					}
			    				
			    				for(int i=3;i<=n;i+=2){
			    					if(prime[i]){
			    						spf[i]=i;
			    						for(int j=2*i;j<=n;j+=i){
			    							
			    							prime[j]=false;
			    						if(spf[j]==1){
			    							spf[j]=i;
			    						}
			    						}
			    					}
			    				}
			    					
			    				}
			    				public static boolean isPrime(long n) {
			    					
			    					if (n <= 1)
			    						return false;
			    					if (n <= 3)
			    						return true;
			    				
			    					if (n % 2 == 0 || n % 3 == 0)
			    						return false;
			    				
			    					for (long i = 5; i * i <= n; i = i + 6)
			    						if (n % i == 0 || n % (i + 2) == 0)
			    							return false;
			    				
			    					return true;
			    				}
			    				
			    				    public static long pow(long n, long p,long mod) {
			    						if(p==0)
			    							return 1;
			    						if(p==1)
			    							return n%mod;
			    						if(p%2==0){
			    							long temp=pow(n, p/2,mod);
			    						return (temp*temp)%mod;
			    						}else{
			    							 	long temp=pow(n,p/2,mod);
			    							 	temp=(temp*temp)%mod;
			    							 	return(temp*n)%mod;
			    							 	
			    						}
			    					}
			    					public static long gcd(long x, long y) {
			    						if (x == 0)
			    							return y;
			    						else
			    							return gcd( y % x,x);
			    					}
			    					
			    					
			    					public static void InputReader(InputStream stream1) {
			    						stream = stream1;
			    					}
			    				 
			    					private static boolean isWhitespace(int c) {
			    						return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
			    					}
			    				 
			    					private static boolean isEndOfLine(int c) {
			    						return c == '\n' || c == '\r' || c == -1;
			    					}
			    				 
			    					private static int read() {
			    						if (numChars == -1)
			    							throw new InputMismatchException();
			    						if (curChar >= numChars) {
			    							curChar = 0;
			    							try {
			    								numChars = stream.read(buf);
			    							} catch (IOException e) {
			    								throw new InputMismatchException();
			    							}
			    							if (numChars <= 0)
			    								return -1;
			    						}
			    						return buf[curChar++];
			    					}
			    				 
			    					private static int nextInt() {
			    						int c = read();
			    						while (isSpaceChar(c))
			    							c = read();
			    						int sgn = 1;
			    						if (c == '-') {
			    							sgn = -1;
			    							c = read();
			    						}
			    						int res = 0;
			    						do {
			    							if (c < '0' || c > '9')
			    								throw new InputMismatchException();
			    							res *= 10;
			    							res += c - '0';
			    							c = read();
			    						} while (!isSpaceChar(c));
			    						return res * sgn;
			    					}
			    				 
			    					private static long nextLong() {
			    						int c = read();
			    						while (isSpaceChar(c))
			    							c = read();
			    						int sgn = 1;
			    						if (c == '-') {
			    							sgn = -1;
			    							c = read();
			    						}
			    						long res = 0;
			    						do {
			    							if (c < '0' || c > '9')
			    								throw new InputMismatchException();
			    							res *= 10;
			    							res += c - '0';
			    							c = read();
			    						} while (!isSpaceChar(c));
			    						return res * sgn;
			    					}
			    				 
			    					private static String nextToken() {
			    						int c = read();
			    						while (isSpaceChar(c))
			    							c = read();
			    						StringBuilder res = new StringBuilder();
			    						do {
			    							res.appendCodePoint(c);
			    							c = read();
			    						} while (!isSpaceChar(c));
			    						return res.toString();
			    					}
			    				 
			    					private static String nextLine() {
			    						int c = read();
			    						while (isSpaceChar(c))
			    							c = read();
			    						StringBuilder res = new StringBuilder();
			    						do {
			    							res.appendCodePoint(c);
			    							c = read();
			    						} while (!isEndOfLine(c));
			    						return res.toString();
			    					}
			    				 
			    					private static int[] nextIntArray(int n) {
			    						int[] arr = new int[n];
			    						for (int i = 0; i < n; i++) {
			    							arr[i] = nextInt();
			    						}
			    						return arr;
			    					}
			    				 
			    					private static int[][] next2dArray(int n, int m) {
			    						int[][] arr = new int[n][m];
			    						for (int i = 0; i < n; i++) {
			    							for (int j = 0; j < m; j++) {
			    								arr[i][j] = nextInt();
			    							}
			    						}
			    						return arr;
			    					}
			    					private static char[][] nextCharArray(int n,int m){
			    						char [][]c=new char[n][m];
			    						for(int i=0;i<n;i++){
			    							String s=nextLine();
			    							for(int j=0;j<s.length();j++){
			    								c[i][j]=s.charAt(j);
			    							}
			    						}
			    						return c;
			    					}
			    				 
			    					private static long[] nextLongArray(int n) {
			    						long[] arr = new long[n];
			    						for (int i = 0; i < n; i++) {
			    							arr[i] = nextLong();
			    						}
			    						return arr;
			    					}
			    				 
			    					private static void pArray(int[] arr) {
			    						for (int i = 0; i < arr.length; i++) {
			    							pw.print(arr[i] + " ");
			    						}
			    						pw.println();
			    						return;
			    					}
			    				 
			    					private static void pArray(long[] arr) {
			    						for (int i = 0; i < arr.length; i++) {
			    							pw.print(arr[i] + " ");
			    						}
			    						pw.println();
			    						return;
			    					}
			    				 
			    					private static void pArray(boolean[] arr) {
			    						for (int i = 0; i < arr.length; i++) {
			    							pw.print(arr[i] + " ");
			    						}
			    						pw.println();
			    						return;
			    					}
			    				 
			    					private static boolean isSpaceChar(int c) {
			    						if (filter != null)
			    							return filter.isSpaceChar(c);
			    						return isWhitespace(c);
			    					}
			    				 
			    					private interface SpaceCharFilter {
			    						public boolean isSpaceChar(int ch);
			    					}
			    				
			    					
			    				}	
			    				
			    				/*class Pair implements Comparable<Pair>{
			
			    					
			    					int  from,to,a,b;
			    					Pair(int from,int to,int a,int b){
			    					
			    						this.from=from;
			    						this.to=to;
			    						this.a=a;
			    						this.b=b;
			    					}
			    					@Override
			    					public int compareTo(Pair o) {
			    				
			    						return 0;
			    						//return (int)(o.size-size);
			    					}
			    					public int hashCode() {
			    							//int hu = (int) (x ^ (x >>> 32));
			    							//int hv = (int) (y ^ (y >>> 32));
			    							//int hw = (int) (mass ^ (mass >>> 32));
			    							//return 31 * hu + hv ;
			    						return 0;
			    						}
			    						public boolean equals(Object o) {
			    							Pair other = (Pair) o;
			    						//	return x == other.x && y == other.y;
			    						return false;
			    						}
			    				}*/
			
