#include <bits/stdc++.h>
using namespace std;

const int INF = 1e+9 * 2;
double eps = 1e-10;

int main() {
	double v;
	while(cin >> v){
		double t = v / 9.8;
		double y = 4.9 * pow(t, 2.0);
		double n = (y + 5) / 5;
		if(n - (int)n < eps)
			cout << (int)n << endl;
		else
			cout << (int)n + 1 << endl;
	}
	return 0;
}