nefu 84

#include <iostream>using namespace std;long long Extended_Gcd(long long a, long long b, long long &x, long long &y){    if(b == 0)    {        x = 1;        y = 0;        return a;    }    long long d = Extended_Gcd(b, a%b, x, y);    long long t = x - (a/b)*y;    x = y;    y = t;    return d;}int main(){    int T;    cin>>T;    long long n,d,x,y;    while(T--)    {        cin>>n>>d>>x>>y;        long long x1,y1,c;        long long k;        c = y - x;        k = Extended_Gcd(d, n, x1, y1);        if(c%k != 0 || d == n)            cout<<"Impossible"<<endl;        else        {            long long s;            s = n/k;            x1 = x1 * (c/k);            x1 = (x1%s + s ) % s;            cout<<x1<<endl;        }    }    return 0;}