#include<cstdio>
#include<iostream>
#include<cstring>
#include<algorithm>
using namespace std;
int main(){
  double v,y,t;
  int n;
  while(cin >> v){
    t = (v/9.8);
    y = 4.9 * (t*t);
    for(int i=1;i<=10000;i++){
      n = 5 * i - 5;
      if((int)y<n){
	cout << i << endl;
	break;
      }
    }
  }
}
 