#include <stdio.h> 
using namespace std;

int nrz(int n) 
{ 
	int nr=0; 
	while(n>=5) 
	{ 
		nr=nr+n/5; 
		n=n/5; 
	} 
	return nr; 
} 

int main() 
{ 
	freopen("fact.in","r",stdin); 
	freopen("fact.out","w",stdout); 
	int p,st,dr,num,m; 
	scanf("%d",&p); 
	st=1; 
	dr=1<<30; 
	while(st<=dr)
	{ 
		m=(st+dr)/2; 
		num=nrz(m); 
		if(num<p) 
			st=m+1; 
		else
			dr=m-1; 
	} 
	if(nrz(st)==p)  
		printf("%d\n",st);
	else
		printf("-1"); 
	return 0; 
}