func_code_string: #include <bits/stdc++.h>   using namespace std;   long long n, m, z, x, c, sum, a[101][101], us[101][101];   char cc, stl;   set<long long> s;   void dfs(long long i, long long j) {     if (a[i][j] == 0 || us[i][j] == 1 || i > n || j > m || i < 1 || j < 1) return;     us[i][j] = 1;     if (s.count(a[i][j]) == 0) sum++, s.insert(a[i][j]);     if (a[i][j] == stl -  A  + 1) {       dfs(i + 1, j);       dfs(i - 1, j);       dfs(i, j + 1);       dfs(i, j - 1);     }   }   int main() {     cin >> n >> m >> stl;     for (int i = 1; i <= n; i++) {       for (int j = 1; j <= m; j++) {         cin >> cc;         if (cc !=  . ) a[i][j] = cc -  A  + 1;         if (cc == stl) z = i, x = j;       }     }     s.insert((int)stl -  A  + 1);     dfs(z, x);     cout << sum <<   n ;   }   