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.util.*;

public class Main {
    static FastScanner in;
    static PrintWriter out;
    static final int MOD = 1000000007;

    public static void main(String[] args) throws IOException {
        //        Scanner in = new Scanner(new File("input.txt"));
        //        Scanner in = new Scanner(System.in);
        //        System.setOut(new PrintStream(new BufferedOutputStream(new FileOutputStream("output.txt")), true));
        out = new PrintWriter(System.out);
        in = new FastScanner(System.in);
        //        in = new FastScanner("input.txt");
        char s[] = in.next().toCharArray();
        int j = 0, k = 0;
        long ans = 0;
        long pow[] = new long[s.length + 1];
        for (int i = 0; i <= s.length; i++) {
            pow[i] = power(2, i);
        }
        while (j < s.length) {
            if (s[j] == 'a')
                k++;
            else {
                ans = (ans + (pow[k] - 1)) % MOD;
            }
            j++;
        }
        out.println(ans);
        out.close();
    }

    /* Iterative Function to calculate (x^y)%p in O(log y) */
    static long power(long x, long y) {
        long res = 1; // Initialize result
        x = x % MOD;
        while (y > 0) {
            if (y % 2 == 1)
                res = (res * x) % MOD;
            y = y / 2;
            x = (x * x) % MOD;
        }
        return res;
    }
}

class Pair {
    public int first; //first member of pair
    public int second; //second member of pair

    public Pair(int first, int second) {
        this.first = first;
        this.second = second;
    }

    public Pair() {

    }
}

class FastScanner {

    BufferedReader br;
    StringTokenizer tokenizer;

    FastScanner(String fileName) throws FileNotFoundException {
        this(new FileInputStream(new File(fileName)));
    }

    FastScanner(InputStream is) {
        br = new BufferedReader(new InputStreamReader(is));
    }

    String nextLine() throws IOException {
        tokenizer = null;
        return br.readLine();
    }

    String next() throws IOException {
        if (tokenizer == null || !tokenizer.hasMoreTokens()) {
            String line = br.readLine();
            if (line == null) {
                return null;
            }
            tokenizer = new StringTokenizer(line);
        }
        return tokenizer.nextToken();
    }

    int nextInt() throws IOException {
        return Integer.parseInt(next());
    }

    long nextLong() throws IOException {
        return Long.parseLong(next());
    }

    double nextDouble() throws IOException {
        return Double.parseDouble(next());
    }

    char nextChar() throws IOException {
        return next().charAt(0);
    }
}