Find eX.cpp

#ifdef DEBUG
#include "debug.h"
#endif // DEBUG
#ifndef DEBUG
template <typename T>
void debug(T &x){}
template <typename T>
void debug(T &x, int i, int j){}
#endif // DEBUG

#include <bits/stdc++.h>

using namespace std;

long long int gcd(long long int a, long long int b){
    if(b == 0) return a;
    return gcd(b, a % b);
}

int main(){
    cin.tie(nullptr), ios::sync_with_stdio(false);
    int T;
    cin >> T;
    while(T--){
        long long int A, B, C, D;
        cin >> A >> B >> C >> D;
        long long int rem = A % B;
        if(B > D) swap(B, D);

        if(rem + 1 != B) cout << "1\n";
        else cout << (B * D / gcd(B, D) - rem) << "\n";
    }
}