#include <iostream>
#include <fstream>

using namespace std;

int main() {
    ifstream in("fact.in");
    ofstream out("fact.out");

    int i = 0;
    int p, ct = 0;

    in >> p;

    if(p == 0)
        out << 1;

    while(p + 1 != ct) {
        if(i % 10 == 5)
            ct++;
        if(i % 10 == 0)
            ct++;
        i++;
    }

    out << i - 1;
}