#include<stdio.h>
int zero(int n){
	int c=0;
	while(n){
		c+=n/5;
		n/=5;
	}
	return c;
}
int main(){
	int n,a,p=1,u=500000000,mij;
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&a);
	while(p!=u){
		mij=(p+u)/2;
		if(zero(mij)>=a)
			u=mij;
		else
			p=mij+1;
	}
	if(zero(p)==a)
		printf("%d\n",p);
	else
		printf("-1\n");
	//printf("%d",zero(a));
	return 0;
}