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.*;
public class Main 
{ 
    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; 
        } 
    } 
    static FastReader s = new FastReader();
    public static void solve(){
        char[] s1 = s.nextLine().toCharArray();
        char[] a = new char[s1.length];
        int index =0;
        int mod = (int)1e9+7;
        for(int i=0;i<s1.length;i++){
            if(s1[i]=='a' || s1[i]=='b'){
                a[index]=s1[i];
                index++;
            }
        }
        Long ans = 1L;
        int count = 0;
        for(int i=0;i<index;i++){
            if(a[i]=='b' && count!=0){
                ans = (ans*(count+1))%mod;
                count = 0;
            }
            else if(a[i]=='a'){
                count++;
            }
        }
        if(count!=0)
            ans = (ans*(count+1))%mod;
        System.out.println(ans-1);
                
    }
    public static void main(String[] args) 
    {  
        int T=1;
        // int T = s.nextInt();
        while(T>0){
            // System.out.println("TEST CASE: "+T);
            solve();
            T--;
        }
    } 
}
