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 Question1{
	static class InputReader {
		public BufferedReader reader;
			public StringTokenizer tokenizer;

			public InputReader() {
				reader = new BufferedReader(new InputStreamReader(System.in));
				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());
			}

			public String nextLine() {
				String s = null;
				try {
					s = reader.readLine();
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
				return s;
			}

			public String nextParagraph() {
				String line = null;
				String ans = "";
				try {
					while ((line = reader.readLine()) != null) {
						ans += line;
					}
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
				return ans;
			}

		}

	public static void main(String args[]){
		InputReader sc=new InputReader();
		PrintWriter pw=new PrintWriter(System.out);
		String str=sc.nextLine();
		int count=0;
		int countOld = count;
		long total=0;
		long mod = (long)Math.pow(10,9)+7;
		long t=1;
		for(int i=0;i<str.length();i++){
			if(str.charAt(i)=='a'){
				count++;
			}else{
				for(int j=countOld;j<count;j++){
					t*=2;
					t%=mod;
				}
				total+=t;
				total%=mod;
				total-=1;
				countOld=count;
			}
		}
		total = total%mod;;
		pw.println(total);
		pw.close();
	}
}