Croc Champ 2013 - Round 2 (Div. 2 Edition) A. Ksusha and Array

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main(){
    int n;
    cin >> n;
    vector<long long> a(n);
    long long minv = 1<<30;
    for(int i = 0; i < n; i++) {
        cin >> a[i];
        minv = min(a[i],minv);
    }
    int i = 0;
    for( i = 0; i < n; i ++ ){
        if(a[i]%minv != 0) break;
    }
    if(i < n) cout<<-1<<endl;
    else cout<<minv<<endl;
    return 0;
}