#include <iostream>
//#include <set>
#include <vector>
#include<numeric>

using namespace std;

int gcd(int x, int y)
{
    if( x == y)
        return x;
    if (x <y)
        return gcd(y,x);
    x%=y;
    if(x == 0)
        return y;
    return gcd(y,x);
}

int main(void)
{
    int n;
    int i;
    int temp;

    vector<int> blanks;
//    multiset<int> blanks;
    
    cin >> n;
    for(i = 0 ; i < n ; i ++){
        cin >> temp;
        blanks.push_back(temp);
    }
//    cout << "t" << endl;
    if(blanks.size() == 0){
        cout << "IMPOSSIBLE" << endl;
    }else{
        int beg = *blanks.begin();
        for(int i = 1; i < n; i++){
            beg = gcd(beg, blanks[i]);
        }
            
        cout <<
            beg
                << endl;

    }
}