#include<iostream>
#include<math.h>

using namespace std;

double getT(double v){return v/9.8;}
double getY(double t){return 4.9*t*t;}

int main()
{
	
	double v,t,y;

	while(cin>>v){
		int N=0;
		t=getT(v);

		y=getY(t);

		while(1){
			if(5*N-5>y)
				break;
			N++;
		}

		cout<<N<<endl;
	}
	return 0;
}