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

int main(void) {
	float v, y, t, n, ans;

  while (cin >> v) {
    t = v / 9.8;
    y = 4.9 * t * t;
    n = (y + 5) / 5;
    ans = (int)n;
    
    if (n - ans > 0.5) ans++;
    cout << ans << endl;
	}
}