#include <iostream>
#include <cmath>

using namespace std;

int main()
{
    double input;

    while (cin >> input) {
        int n = 1;
        while (true) {
            if (10 * n - 10 > input * input / 9.8)
                break;
            n++;
        }

        cout << n << endl;
    }

    return 0;
}