#include<iostream>
#include<math.h>
using namespace std;

int main() {
	float v,t;
	double y;
	
	while ( cin >> v ) {
		t = v / 9.8;
		y = 4.9 * t * t;
		y = (y + 5.0)/5.0;
		
		y = ceil( y );
		
		cout << y << endl;
	}
	return 0;
}