#include<iostream>
#include<math.h>
using namespace std;
int main()
{
		double v, temp, N;
		cin >> v;
		temp = v / 9.8;
		temp = 4.9 * pow(temp,2);
		N = (temp + 5) / 5;
		cout << ceil(N) << endl;
	return 0;
}