#include <iostream>
using namespace std;

int main(){
  double minv;
  while(cin >> minv){
    double t = minv/9.8;
    double height = 4.9 * t * t;
    int floar = height/5 + 1;

    //切り上げ
    double remainder = height % 5;
    if(remainder>0) floar++;
    cout << floar << endl;
  }
  return 0;
}