#include <bits/stdc++.h>
using namespace std;

#define sr srand(time(0));
#define ra(l, h) (rand() % ((h)-(l)+1) + (l))
#define sync { ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL); }
#define ll long long int
#define vi vector<int>
#define fn(n) for(int i = 0; i < n; i++)
#define fr(i, a, b) for(int i = a; i <= b; i++)
#define rfr(i, a, b) for(int i = a; i >= b; i--)
#define pb push_back
#define all(a) a.begin(), a.end()
#define tt int test; cin >> test; while(test--)
#define ff first
#define ss second
#define en cout<< "\n"
#define cy cout << "YES" << endl
#define cn cout << "NO" << endl



int countTrailingZeros(int num) {
    int count = 0;
    while (num % 10 == 0) {
        count++;
        num /= 10;
    }
    return count;
}

bool isPrime(int n) {
    if (n <= 1) {
        return false;
    }
    for (int i = 2; i * i <= n; i++) {
        if (n % i == 0) {
            return false;
        }
    }
    return true;
}


int main() {
    sync
    tt {
        int n;
        cin >> n;
        vi v(n);
        fn(n) cin >> v[i];
    
        int commonZeros = countTrailingZeros(v[0]);

        for (int i = 1; i < n; i++) {
            int trailingZeros = countTrailingZeros(v[i]);
            commonZeros = min(commonZeros, trailingZeros);
        }
        
        // cout << commonZeros << " ";
        
        int ans = 0;
        set<int> rem;
        for(ll k=2; k<pow(10,18); k++){
            if( isPrime(k) ) {
                k = k * pow(10, commonZeros);
                for(int i=0; i<n; i++){
                    rem.insert(v[i]%k);
                }
                if(rem.size() == 2){
                    ans = k;
                    break;
                }
            }
        }
        
        cout << ans << endl;
    }
    return 0;
}