#include <iostream>
#include <cmath>

using namespace std;

void solve()
{
	double v;
	while(cin >> v)
	{
		int N = 2;
		while(true)
		{
			double velocity = 1.4 * sqrt(10.0 * (5 * N - 5));
			if(velocity >= v)
			{
				cout << N << endl;
				break;
			}
			++N;
		}
	}
}

int main()
{
	solve();
	return(0);
}