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

int main()
{
	double minv, v=0.0, y=0.0;
	double t, high = 0.0;
	int f=1;

	while (cin >> minv)
	{
		high = 0;
		t = minv / 9.8;
		y = 4.9 * t * t;
		for (f = 0; high <= y; f++)
		{
			high = f * 5 - 5;
		}
		if (high != y) f--;
		cout << f << endl;
	}
	return 0;
}
