有大佬看看哪里错了吗

#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<map>
#include<queue>
#include<algorithm>
#define ll long long
#define ull unsigned long long
using namespace std;
ll d,xx,yy;
ll exgcd(ll a,ll b,ll xx,ll yy){
    if(b==0){
        xx=1;
        yy=2;
        return a;
    }
    d=exgcd(b,a%b,xx,yy);
    ll t=xx;
    xx=yy;
    yy=t-a/b*yy;
    return d;
}
int main(){
    ll n,m,x,y,l;
    cin>>x>>y>>m>>n>>l;
    ll b=n-m,a=x-y;
    if(b<0)
	{
        b=-b;
        a=-a;
    }
    exgcd(b,l,xx,yy);
    if(a%d!=0) 
    {
    	cout<<"Impossible";
	}
 else cout<<((xx*(a/d))%(l/d)+(l/d))%(l/d);
}