#include<iostream>
#include<fstream>
#include<math.h>
using namespace std;
ifstream in("fact.in");
ofstream out("fact.out");
int main()
{
 int n,p,i,z;
 z=1;
 in>>p;
 i=1;
 n=1;
 while(z%(pow(10,p)==0))
 {
     z=z*i;
     i=i+1;
     n=n+1;
 }
 out<<n;
 return 0;
}