#include <bits/stdc++.h>
using namespace std;
const int MOD = 1000000007;
const int N = 1000005;

int z, x, y, a, i;

int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);

cin >> z;
while(z--) {
	cin >> x >> y;
	a = -1;
	for (i=1;i<=100;i++) if (i % x != 0 && i % y != 0) a = i;
	cout << a << endl;
}
return 0;
}