#include <fstream>

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

int pow5(int n)
{
    int a = 0;
    while(n > 0)
    {
        a += n / 5;
        n /= 5;
    }
    return a;
}

int main()
{
    int n;
    fin >> n;
    int m = n * 5;
    while(pow5(m) != n)
        m -= 5;
    fout << m;
}