aaaaabb
 aabaaaa
 babbabaabbbbabwbvbhbbbaaabbabbbbbbbkabbbbabaaabbbbbbajabbaaabazbbbzbalbabbwbbaabbabacabdbabbbfaaabbb
 baaahbbbba
 ababavvvv
 abnxabbaab
 krflnzhter
 amaabbbbxaabbbabaabaabbaaabaaaaabibbabaabaaabaabcaaxabablbbbbmbbbaaaaaabbaabbbaaabaaaababaababbabbbb
 babbbaaaaaabbbaabaaaaaoaabababaababaaaaababaaaaaaabbbbbbaaapaabaaabaaababaaaabaaaabaaaaababaaaabaaab

5
 14
 42467327
 7
 7
 11
 0
 98718509
 813881762

import java.util.*;
// import java.lang.*;
import java.io.*;

//           THIS TEMPLATE MADE BY AKSH BANSAL.

public class Solution {
    static class FastReader {
        BufferedReader br;
        StringTokenizer st;

        public FastReader() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }

        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }

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

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

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

        String nextLine() {
            String str = "";
            try {
                str = br.readLine();
            } catch (IOException e) {
                e.printStackTrace();
            }
            return str;
        }
    }
    private static int MOD = (int)1e9+7;
    private static boolean[] isPrime;
    private static void primes(){
        int num = (int)1e6; // PRIMES FROM 1 TO NUM
        isPrime = new boolean[num];
     
        for (int i = 2; i< isPrime.length; i++) {
           isPrime[i] = true;
        }
        for (int i = 2; i< Math.sqrt(num); i++) {
           if(isPrime[i] == true) {
              for(int j = (i*i); j<num; j = j+i) {
                 isPrime[j] = false;
              }
           }
        }
    }
    private static long gcd(long a, long b){
        if(b==0)return a;
        return gcd(b,a%b);
    }
    public static void main(String[] args) throws IOException {
        FastReader sc = new FastReader();
        PrintWriter out = new PrintWriter(System.out);
        // primes();
        // ________________________________

        // int t = sc.nextInt();
        // StringBuilder output = new StringBuilder();

        // while (t-- > 0) {
            
        //     output.append(solver()).append("\n");
        // }

        // out.println(output);
        // _______________________________

        String s = sc.nextLine();
        out.println(solver(s));
        // ________________________________
        out.flush();
    }

    public static long solver(String s) {
        long res = 0, multiplier = 0;
        for(int i=0;i<s.length();i++){
            if(s.charAt(i)=='b'){
                multiplier = res;
            }
            else if(s.charAt(i)=='a'){
                res+= multiplier+1;
                res = res%MOD;
            }
        }
        return res;
    }
}