#include <iostream>

using namespace std;

int main() {
    double v, t, y;
    int n;

    while (cin >> v) {
        t = v /9.8;
        y = 4.9 * t * t;
        n = 0;
        while(5 * n - 5 < y) n++;

        cout << n << endl;
    }

}