func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int a[105];     int b[105];     int t, flag, flag1, i, n, c, sum1, sum2;     scanf( %d , &n);     for (i = 1; i <= n; i++) {       scanf( %d , &a[i]);       b[a[i]] = 1;     }     int count = 0;     int sum = 0;     flag = 1;     int d = -1;     c = 0;     for (i = 1; i <= 100; i++) {       if (b[i] == 1) {         count++;         sum += i;         if (c == 0)           c = i;         else {           if (d == -1) {             d = i - c;             c = i;           } else {             if (d != i - c) {               flag = 0;               break;             }             c = i;           }         }       }     }     if (flag == 0) {       printf( -1 n );     } else if (count == 1) {       printf( 0 n );     } else if (count == 2) {       if (sum % 2 == 0) {         sum = sum / 2;         printf( %d n , c - sum);       } else {         sum1 = sum - c;         sum1 = c - sum1;         sum2 = 2 * c - sum;         if (sum1 > sum2) {           sum1 = sum2;         }         printf( %d , sum1);       }     } else if (count == 3) {       sum = sum / count;       printf( %d n , c - sum);     } else {       printf( -1 n );     }     return 0;   }   