#include <iostream>
using namespace std;

int main() {
  double input;

  while(cin >> input){
    double y = input * input / 19.6;
    
    long long int x = max( 1, (int) ( ( y + 5 ) / 5 - 2 ) );
    while ( true ) {
      if ( y <= ( x - 1 ) * 5 ) {
	cout << x << endl;
	break;
      }
      x++;
    }
  }

  return 0;

}