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".
/*
     * For the brave souls who get this far: You are the chosen ones,
     * the valiant knights of programming who toil away, without rest,
     * fixing our most awful code. To you, true saviors, kings of men,
     * I say this: never gonna give you up, never gonna let you down,
     * never gonna run around and desert you. Never gonna make you cry,
     * never gonna say goodbye. Never gonna tell a lie and hurt you.
     * 
     * And Logic is the strongest weapon. 
     *
 */
//package Coding;

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

public class Coding {

    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;
    //pw.print("Case #" + i + ": ");
    //private static int infi = (int) 1e9;
    //private static final int N = 1234567;
    private static final long MOD = (long) 01e9 + 7;
    //Scanner in = new Scanner(new BufferedReader(new InputStreamReader(System.in));

    public static long power(long base, long exponent, long mod) {
        if (base >= mod) {
            base %= mod;
        }
        if (exponent == 0) {
            return 1 % mod;
        }
        long result = power(base, exponent >> 1, mod);
        result = result * result % mod;
        if ((exponent & 1) != 0) {
            result = result * base % mod;
        }
        return result;
    }

    public static int soln() {
        String s = nS();
        int l = s.length();
        int c = 0;
        long ans = 0;
        for (int i = 0; i < l; i++) {
            if (s.charAt(i) == 'a') {
                c++;
            } else {
                ans = (MOD + ans + power(2, c, MOD) - 1);
                while (ans >= MOD) {
                    ans -= MOD;
                }
            }
        }
        pw.println(ans);
        return 0;
    }

    public static void main(String[] args) throws FileNotFoundException {
        InputReader(System.in);
        //pw = new PrintWriter(new FileOutputStream("ans.txt"));
        //pw = new PrintWriter(new FileOutputStream("ans1.txt"));
        pw = new PrintWriter(System.out);
        soln();
        pw.close();
    }

    /*
         *********************************************************************************************
     */
    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 void pIArr(int[] man) {
        int l = man.length;
        for (int i = 0; i < l; i++) {
            pw.print(man[i] + " ");
        }
        pw.println();
    }

    private static void pCArr(char[] man) {
        int l = man.length;
        for (int i = 0; i < l; i++) {
            pw.print(man[i] + " ");
        }
        pw.println();
    }

    private static void pLArr(long[] man) {
        int l = man.length;
        for (int i = 0; i < l; i++) {
            pw.print(man[i] + " ");
        }
        pw.println();
    }

    private static void pDArr(double[] man) {
        int l = man.length;
        for (int i = 0; i < l; i++) {
            pw.print(man[i] + " ");
        }
        pw.println();
    }

    private static double nD() {
        return Double.parseDouble(nS());
    }

    private static int nI() {
        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 nL() {
        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 nS() {
        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 nLi() {
        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 boolean isSpaceChar(int c) {
        if (filter != null) {
            return filter.isSpaceChar(c);
        }
        return isWhitespace(c);
    }

    private interface SpaceCharFilter {

        public boolean isSpaceChar(int ch);
    }
}
