func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     ios_base::sync_with_stdio(false);     cin.tie(NULL);     cout.tie(NULL);     long long n, k;     cin >> n >> k;     string A, B;     cin >> A >> B;     long long ret = 0;     long long ways = 1;     bool isinf = false;     for (auto i = (0); i != (n); ++i) {       if (!isinf) {         ways *= 2;         if (B[i] ==  a ) ways--;         if (A[i] ==  b ) ways--;       }       isinf |= ways > 1e11;       ret += isinf ? k : min(ways, k);     }     cout << ret << endl;     return 0;   }   