poj 1061 青蛙的约会 扩展欧几里德

#include<iostream>
#include<string>
#include<cstring>
#include<algorithm>
#include<cstdio>
using namespace std;
#define ll long long
#define esp 1e-13
const int N=1e4+10,M=1e6+50000,inf=1e9+10,mod=1000000007;
void extend_Euclid(ll a, ll b, ll &x, ll &y)
{
    if(b == 0)
    {
        x = 1;
        y = 0;
        return;
    }
    extend_Euclid(b, a % b, x, y);
    ll tmp = x;
    x = y;
    y = tmp - (a / b) * y;
}
ll gcd(ll a,ll b)
{
    if(b==0)
        return a;
    return gcd(b,a%b);
}
int main()
{
    ll x,y,i,z,t;
    ll n,m,l;
    while(~scanf("%lld%lld%lld%lld%lld",&x,&y,&m,&n,&l))
    {
        ll c=((y-x)%l+l)%l;
        ll a=m-n;
        ll j,k;
        if(c%gcd(a,l)==0)
        {
            extend_Euclid(a,l,j,k);
            ll ans=j*(c/gcd(a,l));
            ans=(ans%(l/gcd(abs(a),l))+(l/gcd(l,abs(a))))%(l/gcd(abs(a),l));
            printf("%lld\n",ans);
        }
        else
            printf("Impossible\n");
    }
    return 0;
}