#include<iostream>
using namespace std;

int main() {
	double v;
	double t, y;
	int n;
	
	while( cin >> v ){
		t = v / 9.8;
		y = 4.9 * t * t;
		n = (y + 4.99999999) / 5 + 1;
		cout << n << endl;
	}
	return 0;
}