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

int main(){
	double a,b,t,y;
	int n;
	while(cin >> a){
		t = a / 9.8;
		y = 4.9 * t * t + 5;
		b = y / 5;
		n = ceil(b);
		cout << n << endl;
	}
	return 0;
}