#include <iostream>
using namespace std;

int main(){
	double v, t, h;
	int ans;
	while(cin >> v){
		t = v / 9.8;
		h = 4.9 * t * t;
		for(int i=1; i<100000;i++){
			if(h < 5*i -5){
				ans = i;
				break;
			}
		}
		cout << ans <<endl;
	}
	return 0;
}