#include<stdio.h>
int p,s,k,i,q,cnt;

int main()
{
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&p);
	s=p;
	if(p!=0)
	{
		for(i=5;s!=0;i+=5)
		{
			q=i;
			cnt=0;
			while(q!=0)
			{
				if(q%5==0)
				{
					cnt++;
					q=q/5;
				}
				else break;
			}
			s=s-cnt;
			if(s<=0) break;
		}
	}
	if(p==0) printf("1");
	if(s<0) printf("-1");
	else printf("%d",i);
	return 0;
}