#include<iostream.h>
#include<fstream.h>
ifstream f("factorial.in");
ofstream g("factorial.out");
int i,j,m,p,ok,t;
int fact(int k) {
 int p=1,i;
 for(j=1;j<=k;j++) p=p*j;
 return p; }
int nr(int k) {int h=k,op=1,l=0;
	while(h && op) {
          		m=h%10;
	           if(m==0) l++;
	            else op=0;
	           h=h/10; }
	return l; }
int n;
	 int main() {
cin>>p;

for(i=5,ok=0;ok==0;i++){
	if(nr(fact(i))==p){  cout<<i;
                        ok=1; } }}