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

int main(){
  double v;
  while (cin >> v) {
    double t = v / 9.8;
    double y = 4.9 * t * t;
    int kai = y / 5;
    if (kai % 5 == 0) {
      kai++;
    } else {
      kai += 2;
    }
    cout  << kai << endl;
  }
}
