#include<iostream>
#define dim 1005
using namespace std;
int n, v[dim];
bool prim(int n)
{
    if (n < 2)
        return false;
    for (int d = 2; d * d <= n; d++)
        if (n % d == 0)
            return false;
    return true;
}
int dei(int st, int dr)
{
    if (st == dr)
        if (prim(v[st]))
            return v[st];
        else return 0;
    else {
        int mid = (st + dr) / 2;
        int s1 = dei(st, mid);
        int s2 = dei(mid+1, dr);
        if (s1 > s2)
            return s1;
        else
            return s2;
    }
}
void read()
{
    cin >> n;
    for (int i = 1; i <= n; i++)
        cin >> v[i];
}
int main()
{
    read();
    cout << dei(1, n);
}