#include <iostream>
using namespace std;

int main(){
	float v;
	while(cin >> v){
		float t = v / 9.8;
		float y = 4.9 * t * t;
		int i = 1;
		while(1){
			if(y <= 5*i-5) break;
			i++;
		}
		cout << i << endl;
	}
	return 0;
}