#include <iostream>
#include <cmath>
using namespace std;

int main() {
    double minSpeed;
    while (cin >> minSpeed) {
        for (int i = 1; ; i++) {
            int y = 5 * i - 5;
            double t = sqrt(y / 4.9);
            double v = 9.8 * t;
            if (v >= minSpeed) {
                cout << i << endl;
                break;
            }
        }
    }
}