#include <fstream>

using namespace std;
ifstream cin ("fact.in");
ofstream cout ("fact.out");
int c;
long long powe;
long long last(unsigned long long nr)
{
    c = 0;
    powe = 5;
    while(powe <= nr)
    {
        c += nr / powe;
        powe *= 5;
    }
    return c;
}

int main()
{
    unsigned long long p, n = 1;
    cin >> p;
    if (p == 0)
    {
        cout << 1;
        return 0;
    }
    while (last(n) != p)
    {
        if (last(n) > p)
        {
            cout << -1;
            return 0;
        }
        n++;
    }
    cout << n;
    return 0;
}