#include <bits/stdc++.h>   using namespace std;   const int MAXN = 1e5 + 5;   const int MOD = 1e9 + 7.5;   char s[MAXN];   int f[MAXN], n;   int main() {     scanf( %s , s + 1);     n = strlen(s + 1);     int preb = 0;     for (int i = 1; i <= n; ++i) {       f[i] = f[i - 1];       if (s[i] ==  a ) {         f[i] = (f[i] + f[preb] + 1) % MOD;       } else if (s[i] ==  b ) {         preb = i;       }     }     cout << f[n] << endl;     return 0;   }   