#include<cstdio>
using namespace std;
long long int a,b,l,k,g,i,o,t,u;
long long int p;
long long lol(long long  v){
	long long int c=5,s=0;
	while(v/c>0){
		s=s+v/c;
		c=c*5;}
	return s;}
int main(){
	unsigned long long int x=2,m,y;
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%lld",&p);
	y=100000000000000ll;
	if(p==0)
		printf("%lld\n",1);
	else{
		while(x<=y && b!=1){
		 m=(x+y)/2;
		 u=lol(m);
		  if(u==p){
			  b=1;
			  k=m;}
		   	else
				if(u>p)
					y=m-1;
				else
					x=m+1;}
		if(b==0)
			printf("%lld\n",-1);
		else
			printf("%lld\n",k-k%5);}
	return 0;}