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

//0024
int main(){
	double v;
	
	while(cin >> v){
		double t=v/9.8;		//g=9.8
		double h=4.9*t*t;	// (1/2) * g * t^2
				
		//5*f-5 > h;
		double f = (h+5)/5;
		cout << ceil(f) << endl;
	}
	return 0;
}