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

int main() {
	int n;
	long double v,y;
	while (cin >> v) {
		y = v * v / 9.8 / 2;
		n = y/5;
		if (n*5 < y)
			n++;
		cout << n + 1 << endl;
	}
	return 0;
}


