#include <iostream>
#include <fstream>
using namespace std;

ifstream fin("fact.in");
ofstream fout("fact.out");

int main()
{
    int n, num = 0, cnt = 1;
    fin >> n;
    while(num != n)
    {
        if(cnt % 5 == 0)
            num ++;
        if(cnt % 10 == 0)
            num ++;
        if(cnt % 25 == 0)
            num ++;
        cnt ++;
    }
    fout << cnt - 1;
}