func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     string s;     cin >> s;     long long mod = 1000000007;     long long sols = 0, ti = 0;     for (int i = s.size() - 1; i >= 0; i--) {       if (s[i] ==  b )         ti++;       else {         sols += ti;         ti *= 2;         sols %= mod;         ti %= mod;       }     }     cout << sols << endl;   }   