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

int main() {
	ios_base::sync_with_stdio( false );

	double v;
	while( cin >> v ) {
		double t = v / 9.8;
		double y = 4.9 * t*t;

		cout << (int)ceil(y / 5) + 1 << endl;
	}
}

