func_code_string: #include <bits/stdc++.h>   using namespace std;   long long inf = 1e9;   int main() {     std::ios::sync_with_stdio(false);     int n;     cin >> n;     long long noemer = 0;     for (long long i = 1; i <= n; i++) {       noemer += (n + 1 - i) * (n + 1 - i);     }     string s1, s2;     cin >> s1;     cin >> s2;     double ans = 0.0;     long long teller = 0;     for (char ch =  A ; ch <=  Z ; ch++) {       long long x, y, z;       x = 0;       y = 0;       z = 0;       for (int i = n - 1; i >= 0; i--) {         if (s2[i] == ch) {           z += n - i;         }       }       x = z;       if (s1[0] == ch) {         if (teller >= inf) {           ans += 1.0 * teller / noemer;           teller = 0;         }         teller += x;       }       for (int i = 1; i < n; i++) {         if (s2[i - 1] == ch) {           y += i;           z -= (n + 1 - i);         }         long long now = x - y + z;         if (s1[i] == ch) {           if (teller >= inf) {             ans += 1.0 * teller / noemer;             teller = 0;           }           teller += now;         }         x = now;       }     }     ans += 1.0 * teller / noemer;     cout << fixed << setprecision(12) << ans << endl;     return 0;   }   