#include<bits/stdc++.h>
using namespace std;
int main(void){
	double v,t;
	double y;
	int ans;
	while(1){
		cin>>v;
		if(cin.eof()==1)	break;
		t=v/9.8;
		y=4.9*pow(t,2);
		y+=5;
		if(fmod(y,5.0)!=0){
			y/=5;
			y++;
		}
		else	y/=5;
		ans=y;
		cout<<ans<<endl;
	}
	return 0;
}
