#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 n = 1;
    while (5 * n - 5 < y) {
      n++;
    }
    cout  << n << endl;
  }
}

