POJ1061 青蛙的约会 扩展欧几里得

#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <string.h>
using namespace std;
typedef long long LL;
const int INF=0x3f3f3f3f;
const int N=5e4+1;
LL exgcd(LL a,LL b,LL& x,LL& y){
if(!b){
x=1;
y=0;
return a;
}
LL d=exgcd(b,a%b,y,x);
y-=a/b*x;
return d;
}
int main(){
LL x,y,m,n,l;
scanf("%I64d%I64d%I64d%I64d%I64d",&x,&y,&m,&n,&l);
LL a=(m-n),b=y-x;
if(a<0)a=-a,b=-b;
a%=l,b%=l;
LL d=exgcd(a,l,x,y);
if(b%d)printf("Impossible\n");
else{
x*=b/d;
LL tmp=l/d;
x=(x%tmp+tmp)%tmp;
printf("%I64d\n",x);
}
return 0;
}