#include <iostream>
#include <cmath>

using namespace std;

int main() {
	double v;
	while (cin >> v){
		double t = v/9.8;
		double y = 4.9*pow(t,2);
		int N;
		for (N=1;;N++) {
			if (5*N-5>=y) break;
		}
		cout << N << endl;
	}
}