扩张欧几里得

#include <iostream>
#include <cstdio>
#include <queue>
#include <algorithm>
#define ll long long

using namespace std;

ll ext_gcd(ll a, ll b, ll &p, ll &q)
{
    ll t, r;

    if(!b){
        p = 1;
        q = 0;
        return a;
    }
    r = ext_gcd(b,a%b,p,q);
    t = p;
    p = q;
    q = t -(a/b)*q;
    return r;
}

int main()
{
    ll x, y, n, m, l;
    ll t, a, b, d, r, c;
    ll p, q;

    scanf("%lld %lld %lld %lld %lld",&x,&y,&n,&m,&l);
    a = n-m;
    c = y-x;
    b = l;
    d = ext_gcd(a,b,p,q);
    if(c%d != 0)
        printf("Impossible");
    else {
        p = p*(c/d);
        p = (p%b+b)%b;
        printf("%lld\n",p);
    }
    return 0;
}

扩张欧几里得