#include <iostream>

using namespace std;

int main(){
  double v;
  while(cin >> v){
    double t,y;
    t=v/9.8;
    y=4.9*t*t;
    y = (y+5.0)/5.0;
    if((y-(int)y)!=0)y+=1.0;
    cout <<(int)y<< endl;
}
return 0;
}