#include <bits/stdc++.h>
using namespace std;
#define debug(a) cerr << #a << " = " << (a) << nl;
#define ll long long
#define int long long
#define nl '\n'

void jAVA()
{
    int a, b; cin >> a >> b;
    if(min(a,b) == 1) cout << -1 << nl;
    else cout << 1 << nl;
}

int32_t main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr); cout.tie(nullptr);

    int t = 1, cs = 0;
    cin >> t;
    while (t--){
        // cout << "Case " << ++cs << ": ";
        jAVA();
    }
    return 0;
}