#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");
int main()
{
    int i,nr,p;
    long long n;
    fin>>n;
    i=0;
    nr=0;
    while(nr<n)
    {
        i=i+5;
        p=i;
        while(p%5==0)
        {
            nr++;
            p=p/5;
        }
    }
    fout<<i;
    return 0;
}