#include <iostream>
using namespace std;
///ifstream in("fact.in");
///ofstream out("fact.out");
int nz(int p){
    int z=0;
    int k=0;
    while(z<p)
    {
        int kk=k;
        while(kk%5==0){
            z++;
            kk=kk/5;
        }
        k++;
    }
    return k;
}
int main()
{
    int p;
    cin>>p;
    cout<<nz(p);
    return 0;
}