#include<iostream>
#include<fstream>
#include<algorithm>

using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int i,j,n,p,x;

int calcul(int i)
{
    int ok=0;
    while(i%5==0)
    {
        i/=5;
        ok++;
    }
    return ok;
}


int main()
{
    fin>>p;
    x=0;
    i=0;
    if(p==0)
    {
        fout<<1;
        return 0;
    }
    while(x<p)
    {
        i+=5;
        x+=calcul(i);
    }
    fout<<i;
    fin.close();
    fout.close();
    return 0;
}