#include <iostream>
#include <cstdio>
using namespace std;

int main(){
  double v,t,y,N;
  while(scanf("%lf",&v) != EOF){
    t = v / 9.8;
    y = t*t * 4.9;
    N=1;
    while(1){
      if(N*5-5 >= y){
	break;
      }
      N++;
    }
    cout << N << endl;
  }
}