#include <bits/stdc++.h>
using namespace std;
ifstream fin("fact.in");
ofstream gout("fact.out");
int main()
{
    long long int n,m,aux;
    int c;
    fin>>n;
    m=0;
    if(n==0)
    {
        gout<<1;
    }
    else
    {
        while(n!=0)
        {
            m=m+5;
            aux=m;
            c=0;
            while(aux%5==0)
            {
                aux=aux/5;
                c++;
            }
            n=n-c;
        }
        gout<<m;
    }
}