aaaaabb
 aabaaaa
 babbabaabbbbabwbvbhbbbaaabbabbbbbbbkabbbbabaaabbbbbbajabbaaabazbbbzbalbabbwbbaabbabacabdbabbbfaaabbb
 baaahbbbba
 ababavvvv
 abnxabbaab
 krflnzhter
 amaabbbbxaabbbabaabaabbaaabaaaaabibbabaabaaabaabcaaxabablbbbbmbbbaaaaaabbaabbbaaabaaaababaababbabbbb
 babbbaaaaaabbbaabaaaaaoaabababaababaaaaababaaaaaaabbbbbbaaapaabaaabaaababaaaabaaaabaaaaababaaaabaaab

5
 14
 42467327
 7
 7
 11
 0
 98718509
 813881762

/*
If you want to aim high, aim high
Don't let that studying and grades consume you
Just live life young
******************************
If I'm the sun, you're the moon
Because when I go up, you go down
*******************************
I'm working for the day I will surpass you
https://www.a2oj.com/Ladder16.html
*/
import java.util.*;
import java.io.*;
import java.math.*;

   public class C
   {
      static long MOD = 1000000007L;
      public static void main(String omkar[]) throws Exception
      {
         BufferedReader infile = new BufferedReader(new InputStreamReader(System.in));  
         StringTokenizer st = new StringTokenizer(infile.readLine());
         String input = st.nextToken();
         input = prune(input);
         int N = input.length();
         if(N == 0)
         {
            System.out.println(0);
            return;
         }
         char[] arr = input.toCharArray();
         ArrayList<Integer> ls = new ArrayList<Integer>();
         char curr = arr[0];
         int size = 1;
         for(int i=1; i < N; i++)
         {
            if(curr == arr[i])
               size++;
            else
            {
               if(curr == 'a')
                  ls.add(size);
               curr = arr[i];
               size = 1;
            }
         }
         if(curr == 'a')
            ls.add(size);
         long res = 1L;
         for(int x: ls)
            res = (res*(x+1))%MOD;
         res--;
         res = (res+MOD)%MOD;
         System.out.println(res);
      }
      public static String prune(String input)
      {
         StringBuilder sb = new StringBuilder();
         for(char c: input.toCharArray())
            if(c == 'a' || c == 'b')
               sb.append(c);
         return sb.toString();
      }
   }