#include <fstream>

using namespace std;

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

int p;

int nrZero(int x)
{
    int rez = 0;
    while(x >= 5)
    {
        rez += x / 5;
        x/=5;
    }
    return rez;
}

int main()
{
    long long rez = 0;
    in >> p;
    long long pas = 1 << 28;
    while(pas)
    {
        if(nrZero(rez+pas) < p)
        {
            rez += pas;
        }
        pas /= 2;
    }
    rez++;
    if(nrZero(rez) != p)
        return -1;
    out << rez << '\n';
    return 0;
}