aaaaabb
 aabaaaa
 babbabaabbbbabwbvbhbbbaaabbabbbbbbbkabbbbabaaabbbbbbajabbaaabazbbbzbalbabbwbbaabbabacabdbabbbfaaabbb
 baaahbbbba
 ababavvvv
 abnxabbaab
 krflnzhter
 amaabbbbxaabbbabaabaabbaaabaaaaabibbabaabaaabaabcaaxabablbbbbmbbbaaaaaabbaabbbaaabaaaababaababbabbbb
 babbbaaaaaabbbaabaaaaaoaabababaababaaaaababaaaaaaabbbbbbaaapaabaaabaaababaaaabaaaabaaaaababaaaabaaab

5
 14
 42467327
 7
 7
 11
 0
 98718509
 813881762

import java.io.*;
import java.util.*;

public class C_The_Fair_Nut_and_String{
    static int MOD = (int)1e9+7;
    
    @SuppressWarnings("unchecked")
    public static void main(String[] args) throws Exception{
        char[] str = in.readLine().toCharArray();
        int[] rgt = new int[str.length];
        int n = rgt.length;
        /**
         * abaaba
         * 6 22 1
         */
        int b = 0, psum = 0;
        for(int i = n-1; i >= 0; i--){
            if(str[i] == 'b'){
                rgt[i] = psum;
                b = psum;                
            }
            else{
                rgt[i] = b + 1;
                psum = add(psum , rgt[i]);
            }
        }
        int ans = 0;
        for(int i = 0; i < n; i++){
            if(str[i] == 'a')
                ans = add(ans, rgt[i]);
        }
        // System.out.println(Arrays.toString(rgt));
        System.out.println(ans);
    }
    public static int add(int a,int b){
        return (a + b)%MOD;
    }

    static Inputer in;
    static {
        in = new Inputer();
    }

    static class Inputer{
        BufferedReader br;
        Inputer(){
            try{
                br = new BufferedReader(new InputStreamReader(System.in));
            }
            catch(Exception e){}
        }
        public int readInt() throws Exception{
            return Integer.parseInt(readLine());
        }
        public long readLong() throws Exception{
            return Long.parseLong(readLine());
        }
        public int[] readA(String delim) throws Exception{
            String[] s = readLine().split(delim);
            int[] A = new int[s.length];
            for(int i = 0; i < s.length; i++)
                A[i] = Integer.parseInt(s[i]);
            return A;
        }
        public int[] readA() throws Exception{
            String[] s = readLine().split("\\s+");
            int[] A = new int[s.length];
            for(int i = 0; i < s.length; i++)
                A[i] = Integer.parseInt(s[i]);
            return A;
        }
        public long[] readLA() throws Exception{
            String[] s = readLine().split("\\s+");
            long[] A = new long[s.length];
            for(int i = 0; i < s.length; i++)
                A[i] = Long.parseLong(s[i]);
            return A;
        }
        public String readLine() throws Exception{
            return br.readLine();
        }
        public int[] copyA(int[] A){
            int[] B = new int[A.length];
            for(int i= 0 ; i < A.length; i++)
                B[i] = A[i];
            return B;
        }
    }
    static void shuffle(int[] A){
        int n = A.length;
        Random rand = new Random();
        for(int t = 0; t < A.length; t++){
            int i1 = rand.nextInt(n);
            int i2 = rand.nextInt(n);
            int tmp = A[i1];
            A[i1] = A[i2];
            A[i2] = tmp;
        }
    }
    static class Pair{
        int first, second;
        Pair(){
        }
        Pair(int a, int b){
            first = a;
            second = b;
        }
        @Override
        public String toString() {
            return "{"+first+","+second+"}";
        }
    }
}