#include<iostream>
#include<algorithm>
#include<string>
#include<cmath>
using namespace std;
int main(){
  int N=1,b=0,t,j;
  double a,v,y,i;
  while(cin >> a){
    N=1;
    b=0;
    i=a/9.8;
    y=4.9*i*i;
    while(b<y){
      b=5*N-5;
      N++;
    }
    N--;
    cout << N << endl;
  }
}