bzoj1477: 青蛙的约会

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;
#define rep(i,s,t) for(int i=s;i<=t;i++)
#define clr(x,c) memset(x,c,sizeof(x))
#define ll long long
ll read(){
	ll x=0;char c=getchar();
	while(!isdigit(c)) c=getchar();
	while(isdigit(c)) x=x*10+c-‘0‘,c=getchar();
	return x;
}
ll gcd(ll a,ll b){
	return b?gcd(b,a%b):a;
}
void exgcd(ll a,ll b,ll &x,ll &y){
	if(!b){
		x=1,y=0;return ;
	}
	exgcd(b,a%b,x,y);
	ll temp=x;x=y;y=temp-a/b*y;
}
int main(){
	ll x=read(),y=read(),m=read(),n=read(),l=read();
	ll a=n-m,b=l,c=x-y;
	ll Gcd=gcd(a,b);
	if(c%Gcd) {
		printf("Impossible\n");return 0;
	}
	a/=Gcd,b/=Gcd,c/=Gcd;
	exgcd(a,b,x,y);
	x=((c*x)%b+b)%b;
	printf("%lld\n",x);
	return 0;
}