func_code_string: #include <bits/stdc++.h>   using namespace std;   int a[110], b[110], cnt, n;   map<int, int> mp;   int main() {     scanf( %d , &n);     for (int i = 1; i <= n; i++) {       int num;       scanf( %d , &num);       if (!mp[num]) {         mp[num]++;         b[cnt++] = num;       }     }     sort(b, b + cnt);     if (cnt == 1)       printf( 0 );     else if (cnt == 2) {       if (abs(b[1] - b[0]) % 2)         printf( %d , abs(b[1] - b[0]));       else         printf( %d , abs(b[1] - b[0]) / 2);     } else if (cnt == 3 && ((b[1] - b[0]) == (b[2] - b[1])))       printf( %d , b[1] - b[0]);     else       printf( -1 );     return 0;   }   