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.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.BitSet;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Random;
import java.util.Set;
import java.util.Stack;
import java.util.StringTokenizer;
import java.util.TreeMap;
import java.util.TreeSet;
import java.util.Vector;
import java.util.regex.Matcher;
import java.util.regex.Pattern;



public class HR20B {

    static StringTokenizer st;
    static BufferedReader br;
    static PrintWriter pw;

    static class Sort implements Comparable<Sort> {
        int ind, a;

        @Override
        public int compareTo(Sort o) {
            return a - o.a;
        }
        public Sort(int i, int an) {
            ind = i;
            a = an;
        }
    }

    public static void main(String[] args) throws IOException {
        br = new BufferedReader(new InputStreamReader(System.in));
        pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
        solve();
        pw.close();
    }
    
    private static void solve() throws IOException {
    	char[] a = next().toCharArray();
    	long ans = 0, cb = 0;
    	long mod = 1000000007L;
    	for (int i = a.length - 1; i >= 0; --i) {
    		if (a[i] == 'b') {
    			cb = (cb + 1) % mod;
    		} else {
    			ans = (ans + cb) % mod;
    			cb = (cb + cb) % mod;
    		}
    	}
    	pw.println(ans);
    }

	private static int sumf(int[] fen, int id) {
        int summ = 0;
        for (; id >= 0; id = (id & (id + 1)) - 1)
            summ += fen[id];
        return summ;
    }

    private static void addf(int[] fen, int id) {
        for (; id < fen.length; id |= id + 1)
            fen[id]++;
    }

    private static int nextInt() throws IOException {
        return Integer.parseInt(next());
    }
    private static long nextLong() throws IOException {
        return Long.parseLong(next());
    }
    private static double nextDouble() throws IOException {
        return Double.parseDouble(next());
    }
    private static String next() throws IOException {
        while (st==null || !st.hasMoreTokens())
            st = new StringTokenizer(br.readLine());
        return st.nextToken();
    }
}