#include <iostream>
#include <fstream>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int main()
{ int p,n,s,k;
    fin>>p;
        if (p>=0 && p<=100000000){
            n=1;
                while (n <=p || s != p){
                    s=0;
                    for (int i=1;i<=n;i=i+1){
                        n=n*i;
                    }
                    while (n != 0 && k==1) {
                         k=1;
                        if (n%10 == 0)s=s+1;
                        else k=0;
                            n=n/10;
                    }
                    n=n+1;
                }
        }
      fout<<s;

    return 0;
}