#include <fstream>
#include <cstdio>

int getFiveFactorCount(int n) {
	int count = 0;
	while (n)
		count += (n /= 5);
	return count;
}

int factorial(int p) {
	int position = 1, offset = 0, best = -1;
	if (p == 0)
		return position;
	for (offset = 1; offset < 5 * p; offset *= 2)
		continue;

	for (offset /= 2; offset; offset /= 2) {
		int zeros = getFiveFactorCount(position + offset);
		if (zeros == p)
			best = position + offset;
		else if (p > zeros)
			position += offset;
  }
	if (getFiveFactorCount(position) == p)
		return position;
	return best;
}

int main() {
	char const * const inputFile = "fact.in",
						 * const outputFile = "fact.out";
	std::ifstream in(inputFile);
	std::ofstream out(outputFile);

	int p = 0;
	while (in >> p)
		out << factorial(p) << std::endl;
	return 0;
}