#include<stdio.h>
int fact(int n){
	int c=0;
	while(n){
		c+=n/5;
		n/=5;
	}
	return c;
}
int main () {
	int k,p,u,m;
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&k);
	p=1;
	u=800000000;
	while(p!=u){
		m=(p+u)/2;
		if(fact(m)<k)
			p=m+1;
		else
			u=m;
	}
	if(k==fact(p))
		printf("%d\n",p);
	else
		printf("-1\n");
	return 0;
}