func_code_string: #include <bits/stdc++.h>   using namespace std;   char s[200001];   long long a[26];   long long cnt = 0;   int main() {     long long i, j, k, l, m, n, t;     cin >> t;     cin >> s;     l = strlen(s);     for (i = 0; i < 26; i++) a[i] = 0;     for (i = 1; i < l; i = i + 2) {       if ((s[i - 1] - 97) != (s[i] - 65)) {         if (a[s[i] - 65] > 0) {           a[s[i] - 65]--;           a[s[i - 1] - 97]++;         } else {           cnt++;           a[s[i - 1] - 97]++;         }       }     }     cout << cnt << endl;     return 0;   }   