#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int nrZerouri(long int a) {
	int sum = 0;
	while (a != 0) {
		int rest = a % 10;
		if (rest == 0) sum++; else
			break;
		a /= 10;
	}
	return sum;
}
long int fact(int n) {
	if (n >= 1) { return n * fact(n - 1); }
	else { return 1; }
}

int main()
{
	int a;
	cin >> a;
	int zerouri[1000];
	string s;
	for (int i = 1; i <= 100; i++) {
		if (nrZerouri(fact(i)) == a) {
			cout << i; break;
		}
	}
	getline(cin, s);
	cin.get();
	return 0;
	
}