#include <fstream>
#include <iostream>
#include <math.h>

using namespace std;

unsigned long divizori(unsigned long &x)
{
     unsigned long putere=0,cinci=0;
     while (cinci*5+1<=x){cinci=cinci*5+1; putere=putere+1;}

     x=x-cinci;

     return (unsigned long)ceil(pow(5,putere));
     }

int main()
{
    unsigned long p,n,aux;
    ifstream f("fact.in");
    f>>p;

    n=0;
unsigned long adun;

if (p==0) n=1;
else
while (p>0)
 {adun=divizori(p);
  n=n+adun;
}
  // if (p<0) n=-1;


ofstream g("fact.out");
 g<<n;

      return 0;
}