#include <bits/stdc++.h>   using namespace std;   int main() {     int t;     cin >> t;     int arr[t];     for (int i = 0; i < t; i++) {       int y;       cin >> y;       y = y + i;       arr[i] = y;     }     sort(arr, arr + t);     for (int i = 0; i < t; i++) {       arr[i] -= i;     }     int check = 1;     for (int i = 0; i < t - 1; i++) {       if (arr[i] > arr[i + 1]) {         check = 0;         break;       }     }     if (check == 0)       cout <<  :(  n ;     else {       for (int i = 0; i < t; i++) {         cout << arr[i] <<    ;       }     }     return 0;   }   