#include <fstream>
using namespace std;

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

long long p;

long long zeros(long long n) {
    long long cnt = 0;
    while (n != 0) {
        n /= 5;
        cnt += n;
    }
    return cnt;
}

int main()
{
    fin >> p;

    if (p == 0) {
        fout << 1;
        return 0;
    }

    long long st = 0, dr = 5 * p;

    while (st <= dr) {
        long long mid = (st + dr) / 2;

        if (zeros(mid) < p) {
            st = mid + 1;
        } else {
            dr = mid - 1;
        }
    }

    if (zeros(st) == p) {
        fout << st;
    } else {
        fout << -1;
    }
    return 0;
}