#include <fstream>

using namespace std;

ifstream inFile("fact.in");
ofstream outFile("fact.out");

int nr_zeroes(int x)
{
	int i = 5, n = 0;
	while(x/i){
		n += x/i;
		i *= 5;
	}
	return n;
}

int main() 
{

	int p;

	inFile >> p;

	for(int i = 1; ;i++){
		if(nr_zeroes(i) == p){
			outFile << i;
			return 0;
		}

		if(nr_zeroes(i) > p){
			return 0;
		}

	}
}