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.StringTokenizer;

//solution classes here

public class Code {

    //main solution here

    static Scanner sc = new Scanner(System.in);
    static PrintWriter out = new PrintWriter(System.out);
    static long mod = (long)1e9+7;//998244353
    //static ArrayList<Integer> list[] = new ArrayList[(int)1e6+1];
    //static int color[] = new int[(int)1e6+1];
    //static int visit[] = new int[(int)1e5+1];
    //static Deque<Integer> q = new ArrayDeque<>();
    public static void main(String[] args) throws IOException {
        String s = sc.next();
        int n = s.length();
        char[] ch = s.toCharArray();
        long intial = 0;
        for(int i=0;i<n;i++) {
            if(ch[i]=='b')
                intial++;
        }
        long nb=0;
        for(int i=n-1;i>=0;i--) {
            if(ch[i]=='b')
                nb=(nb+1)%mod;
            else {
                nb=(nb*2)%mod;
            }
        }
        long ans=(nb-intial)%mod;
        out.println(ans);


        out.flush();
        out.close();
    }
    //solution functions here

    static class Scanner {
        StringTokenizer st;
        BufferedReader br;

        public Scanner(InputStream s) {
            br = new BufferedReader(new InputStreamReader(s));
        }

        public Scanner(FileReader fileReader) {
            br = new BufferedReader(fileReader);
        }

        public String next() throws IOException {
            while (st == null || !st.hasMoreTokens())
                st = new StringTokenizer(br.readLine());
            return st.nextToken();
        }

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

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

        public String nextLine() throws IOException {
            return br.readLine();
        }

        public boolean ready() throws IOException {
            return br.ready();
        }
    }
}

/* *****************************************************************************************************************************
 * I'M NOT IN DANGER, I'M THE DANGER!!!
 * *****************************************************************************************************************************
 */