#include <iostream>
#include <cmath>

using namespace std;

int main()
{
        double v;

        while (cin >> v) {
                double t = v / 9.8;
                double y = 4.9 * t * t;
                double n = (y + 5) / 5;
                cout << (int)ceil(n) << endl;
        }

        return 0;
}