#include <fstream>

using namespace std;

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

int zero(int n)
{
    int sum = 0;

    while(n)
    {
        sum += n / 5;
        n /= 5;
    }

    return sum;
}

int main()
{
    int p, n, i, pas;

    in>>p;

    i = 0;
    pas = 1 << 30;
    while(pas)
    {
        if(zero(i + pas) < p)
            i += pas;
        pas /= 2;
    }

    if(zero(i + 1) == p)
        out<<i + 1;
    else
        out<<-1;
    return 0;
}