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

int p1;

int nr0(int a)
{
    long s = 0;
    long b = 5;
    while (a >= b) {
        s += a/b;
        b *= 5;
    }
    return s;
}

int main()
{
    f>>p1;
    int ls = 0, ld = 400000015, n = (ls + ld) / 2;

    while(nr0(n) != p1 && ld > ls)
    {
        int zero = nr0(n);
        if(zero > p1)
            ld = n;
        else
            ls = n;
        n = (ls + ld)/2;
    }

    while(nr0(n - 1) == p1 && n > 1)
        n--;

    if(nr0(n) == p1)
        g<<n;
    else
        g<<-1;

    return 0;
}