#include <bits/stdc++.h>
using namespace std;

int main()
{
  double v, y;

  while (cin >> v){
    double t = 0;
    int floor = 1;
    while (9.8 * t < v) t += 0.1;
    y = 4.9 * t * t;
    for (; (floor * 5) - 5 < y; floor++){}
    printf("%d\n", floor);
  }
}