#include <iostream>
#include <fstream>
#include <climits>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");

long cautarebinara(int n)
{
    long p=1, u=400000000;int m;
    while(p <= u)
    {
        m = (p + u) / 2;
        int nr0=m/5+m/25+m/125+m/625+m/3125+m/15625+m/78125+m/390625+m/1953125+m/9765625+m/48828125+m/244140625;
        if(nr0==n)
            {
                while(m%5!=0)m--;
                return m;}
        if(nr0<n)
            p = m + 1;
        else
            u = m - 1;
    }
    return -1;
}

int main()
{
    int p;
    f>>p;
    g<<cautarebinara(p);
    return 0;
}