#include <iostream>

using namespace std;

void storey(double);

int main() {

	double min;

	while(cin>>min) {
		storey(min);
	}

	return 0;

}

void storey(double min) {

	double t, y, N;

	t=min/9.8;
	y=4.9*t*t;

	N=y/5+1;
	N+=0.9;
	N=(int)N;

	cout << N << endl;

}