#include <fstream>
using namespace std;

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

int binary_search(int lo, int hi, int x);
int count_zeros(int x);

int main() 
{
	int p;
	fin >> p; 
	if (p == 0) {
		fout << 1;
	} else {
		fout << binary_search(1, 6 * p, p);
	}
}

int binary_search(int lo, int hi, int x) {
	while (lo < hi) {
		int mid = lo + (hi - lo) / 2;
		int numZeros = count_zeros(mid);
		if (numZeros == x && mid % 5 == 0) {
			return mid;
		} else if (numZeros < x) {
			lo = mid + 1;
		} else {
			hi = mid;
		}
	}
	if (lo >= hi) {
		return -1;
	}
}

int count_zeros(int x) {
	int result = 0, five = 5;
	while (x / five > 0) {
		result += x / five;
		five *= 5;
	}
	return result;
}