#include<iostream.h>
int main(){
	long int x,y,m,n,l,z,d,count;
	long f(long,long,long);
	cin>>x>>y>>m>>n>>l;
	z=(y-x)%l;
	if(z){
		if(m==n){
			count=-1;
		}
		else{
			if(n>m){
				z=l-z;
				d=(n-m)%l;
			}
			else 
				d=(m-n)%l;
			count=f(z,d,l);
		}
	}
	else
		count=0;
	if(count<0)cout<<"Impossible"<<endl;
	else cout<<count<<endl;
	return 0;
}

long f(long z,long d,long l){
	long count,k;
	if(d){
		if(z%d==0){
			count=z/d;
			return count;
		}
		else {
			long d0=d;
			long z0=z;
			z=d0-z%d0;
			d=l%d0;			
			k=f(z,d,d0);
			if(k>0)
				count=(z0+k*l)/d0;
			else 
				return -1;
			return count;
		}
	}
	else 
		return -1;
}

• 我不知道你是用什么方法做，其实这题只需要判断公约数就可以了 (791) hudedi 2006-05-29 18:15:42