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".

/*


        HARSH KHATRI
        DA-IICT

                      */

import java.io.*;
import java.util.*;
import java.lang.*;
import java.util.Scanner;
import java.util.Arrays;
import java.util.List;
import java.util.ArrayList;

public class CF805D {

    static long pow(long a, long n, long m) {
        long res = 1;

        while(n>0) {
            if((n&1)==1) {
                res = (res*a)%m;
            }
            a = (a*a)%m;
            n >>=1;

        }

        return res;
    }

    public static void main(String[] args) {

        FasterScanner in = new FasterScanner();
        String s = in.nextLine();
        int n = s.length(), i, j, c1=0, c2=0;
        long ans = 0, m = 1000000007, p;
        boolean hasB = false; char c;

        for(i=0; i<n; i++) {
            c = s.charAt(i);
            if(!hasB && c=='a'){
                c1++;
            }
            else if(hasB && c=='a') {
                p = pow(2, c1, m);
                if(p==0) p=m;
                p--; p *= c2; p%=m;
                ans = (ans+p);
                ans %= m;
                c1++;
                c2 = 0;
                hasB = false;
            }
            else if(c=='b') {
                c2++;
                hasB = true;
            }
        }

        if(hasB) {
            p = pow(2, c1, m);
            if(p==0) p=m;
            p--; p*= c2; p%=m;
            ans = (ans+p);
            ans %= m;
        }

        System.out.println(ans);

    }
}



class FasterScanner {
    private byte[] buf = new byte[1024];
    private int curChar;
    private int snumChars;

    public int read() {
      if (snumChars == -1)
    throw new InputMismatchException();
      if (curChar >= snumChars) {
    curChar = 0;
    try {
      snumChars = System.in.read(buf);
    } catch (IOException e) {
      throw new InputMismatchException();
    }
    if (snumChars <= 0)
      return -1;
      }
      return buf[curChar++];
    }

    public double nextDouble() {
      return Double.parseDouble(this.nextString());
    }

    public 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();
    }

    public String nextString() {
      int c = read();
      while (isSpaceChar(c))
    c = read();
      StringBuilder res = new StringBuilder();
      do {
    res.appendCodePoint(c);
    c = read();
      } while (!isSpaceChar(c));
      return res.toString();
    }

    public 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;
    }

    public 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;
    }

    public int[] nextIntArray(int n) {
      int[] arr = new int[n];
      for (int i = 0; i < n; i++) {
    arr[i] = nextInt();
      }
      return arr;
    }

    public long[] nextLongArray(int n) {
      long[] arr = new long[n];
      for (int i = 0; i < n; i++) {
    arr[i] = nextLong();
      }
      return arr;
    }

    private boolean isSpaceChar(int c) {
      return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
    }

    private boolean isEndOfLine(int c) {
      return c == '\n' || c == '\r' || c == -1;
    }
}