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

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

int main() {
	long double v;
	while(cin >> v){
		long double n = (4.9 * pow(v / 9.8, 2.0) + 5.0) / 5.0;
		if(n - (int)n < eps)
			cout << (int)n << endl;
		else
			cout << (int)n + 1 << endl;
	}
	return 0;
}