#include<fstream>
using namespace std;
ifstream f("factorial.in");
ofstream g("factorial.out");
int i,n,u,m,z,k;
long long p,s;
int main (){
	f>>k;
    p=1;
	u=1000000000;
	if(k==0){
		g<<1;
		return 0;
	}
	while (p<=u){
		m=(p+u)/2;
		z=5;
		s=0;
			while (z<=m){
				s=s+m/z;
				z=z*5;
			}
			if (s==k){
				while(m%5!=0)
					 m--;
				g<<m;
				break;
			}
			else
				if(s<k)
					  p=m+1;
				else
					 u=m-1;
				
	}			
			
if(p>u)
g<<-1;
return 0;
}