#include <fstream>
using namespace std;
ifstream f("fact.in");
ofstream g("fact.out");
int cautare(int n) {
	int count = 0;
	int ls = 1;
	int ld = 500000000;
	int mid;
	int putere;
	while (ls <= ld) {
		count = 0;
		mid = (ls + ld) / 2;
		for (putere = 5; putere <= mid; putere *= 5) {
			count += mid / putere;

		}
		if (count == n)
			return mid - mid % 5;

		if (count > n)
			ld = mid - 1;
		if (count < n)
			ls = mid + 1;

	}
	return -1;
}

int main()
{
	int n;
	f >> n;
	g << cautare(n) << endl;
	return 0;
}