#include<iostream>
#include<cmath>
#include<cstdio>
using namespace std;
int main()
{
	double v;
	double t , y , n;
	while ( cin >> v )
	{
		t = v / 9.8;
		y = 4.9*t*t;
		n = ( y + 5 ) / 5;
		printf("%.0f\n" , n);
	}
}