#include <iostream>
using namespace std;

int main() {
    int M, N, n, t;
    int timee;
    int x, y, w, z;
    int is_valid = 0;
    cin >> n;
    for(t=0; t<n; t++){
        cin >> M >> N >> w >> z ;
        is_valid = 0;
        timee = 1;
        for(x=1, y=1; !((x == M) && (y == N));){
            if(x<M){
                x++;
            }else{
                x = 1;
            }
            if(y<N){
                y++;
            }else{
                y = 1;
            }
            timee++;

            if((x == w) && (y == z)){
                is_valid = 1;
                cout << timee << "\n";
                continue;
            }
        }
        if(is_valid == 0){
            cout << -1 << "\n";
        }
    }
    return 0;
}