#include <fstream>


using namespace std;


ifstream cin("fact.in");
ofstream cout("fact.out");


int p, answer;


int numarZerouri(int x) {
	int putere = 5, returnValue = 0;
	while (putere <= x) {
		returnValue += x / putere;
		putere *= 5;
	}
	return returnValue;
}


void read() {
	cin >> p;
}


void solve() {
	int stanga = 1, dreapta = 1e9, mijloc;
	while (stanga <= dreapta) {
		mijloc = (stanga + dreapta) / 2;
		if (numarZerouri(mijloc) >= p) {
			answer = mijloc;
			dreapta = mijloc - 1;
			continue;
		}
		stanga = mijloc + 1;
	}
}


void display() {
	cout << answer;
}


int main() {
	read();
	solve();
	display();
	return 0;
}