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.util.*;
import java.io.*;
import java.math.*;

public class Main{
  /*
  .
  .
  .
  .
  .
  .
  .
  some constants
  .
  */
  /*
  .
  .
  .
  if any
  .
  .
  */
  public static void main(String[] args) throws IOException{
		/*
		.
		.
		.
		.
		.
		.
    */
    char arr[]=ns().toCharArray();
    long ans=0;
    int power[]=new int[1000000+1];
    int max=1000000+1;
    int len=arr.length;
    int n=0;
    int i,j;
    power[0]=1;
    for(i=1;i<max;i++){
      power[i]=(2*power[i-1])%mod;
    }
    for(i=0;i<len;i++){
      if(arr[i]=='a'){
        n++;
      }
      else{
        ans += (power[n]-1+mod)%mod;
      }
      ans %=mod;
    }
    sop(ans);
    /*
		.
		.
		.
		.
		.
		.
		.
		*/
	}
	/*
	temporary functions
	.
	.
	*/
	/*
	fuctions
	.
	.
	.
	.
	.
	.
	.
	.
	.
	.
	.
	.
	.
	.
	.
	.
	.
	abcdefghijklmnopqrstuvwxyz
	.
	.
	.
	.
	.
	.
	*/
	static int modulo(int j,int m){
		if(j<0)
			return m+j;
		  if(j>=m)
			return j-m;

			return j;
	}
	static final int mod=1000000007;
	static final double eps=1e-8;
	static final long inf=100000000000000000L;
	static final boolean debug=true;
	static Reader in=new Reader();
	static StringBuilder ansa=new StringBuilder();
	static long powm(long a,long b,long m){
		long an=1;
		long c=a;
		while(b>0){
			if(b%2==1)
				an=(an*c)%m;
			c=(c*c)%m;
			b>>=1;
		}
		return an;
	}
	static Random rn=new Random();
	static void sop(Object a){System.out.println(a);}
	static int ni(){return in.nextInt();}
	static int[] nia(int n){int a[]=new int[n];for(int i=0;i<n;i++)a[i]=ni();return a;}
	static long nl(){return in.nextLong();}
	static long[] nla(int n){long a[]=new long[n];for(int i=0; i<n; i++)a[i]=nl();return a;}
	static String ns(){return in.next();}
	static String[] nsa(int n){String a[]=new String[n];for(int i=0; i<n; i++)a[i]=ns();return a;}
	static double nd(){return in.nextDouble();}
	static double[] nda(int n){double a[]=new double[n];for(int i=0;i<n;i++)a[i]=nd();return a;}
	static class Reader{
		public BufferedReader reader;
		public StringTokenizer tokenizer;
		public Reader(){
			reader=new BufferedReader(new InputStreamReader(System.in),32768);
			tokenizer=null;
		}
		public String next(){
			while(tokenizer==null || !tokenizer.hasMoreTokens()){
				try{
					tokenizer=new StringTokenizer(reader.readLine());
				}
				catch(IOException e){
					throw new RuntimeException(e);
				}
			}
			return tokenizer.nextToken();
		}
		public int nextInt(){
			return Integer.parseInt(next());
		}
		public long nextLong(){
			return Long.parseLong(next());
		}
		public double nextDouble(){
			return Double.parseDouble(next());
		}
	}
}
