#include <iostream>
#include <cmath>

using namespace std;

int main (void) {
    while (1) {
        double v0, v;
        cin >> v0;
        if (cin.eof()) break;
        for (int n = 0; ; n++) {
            v = 9.8 * sqrt((5 * n - 5) / 4.9);
            if (v >= v0) {
                cout << n << endl;
                break;
            }
        }
    }
    return 0;
}