12184

12184

#include <iostream>
#include <vector>

#define INFINITY 9E18
#define IMPOSSIBLE "impossible"

using namespace std;

typedef vector<long long> vll;

long long GCD(long long a, long long b) {
    long long c;
    while (a != 0) {
        c = a; a = b % a;  b = c;
    }
    return b;
}

int main() {
    int T;
    int C;
    int aux;
    long long minSerial;
    bool possible;
    long long N;
    long long maxComunDivisor;
    long long maxA10;
    int c;
    int i;
    int t;

    cin >> T;
    for (t = 0; t < T; t++) {
        cin >> C;
        maxA10 = 0;
        minSerial = INFINITY;
        vll serials(C, 0);
        for (c = 0; c < C; c++) {
            for (i = 0; i < 9; i++) {
                cin >> aux;
                serials[c] += aux;
            }
            cin >> aux;
            serials[c] -= aux;
            if (aux > maxA10)  maxA10 = aux;
            if (serials[c] < minSerial) minSerial = serials[c];
        }

        // Caso base 1: min <= 1.
        if (minSerial <= 1) {
            cout << IMPOSSIBLE << endl;
        } else {
            maxComunDivisor = serials[0];
            for (c = 1; c < C; c++) {
                maxComunDivisor = GCD(maxComunDivisor, serials[c]);
            }

            possible = (maxComunDivisor > 1 && maxComunDivisor > maxA10);

            if (!possible) {
                cout << IMPOSSIBLE << endl;
            } else {
                cout << maxComunDivisor << endl;
            }
        }
    }

}