#include<cstdio>

using namespace std;
int main(void)
{
	double t,v,y,i;
	while(scanf("%lf",&v) != EOF)
	{
		t = v / 9.8;
		y = 4.9 * t *t;

		for(i = 0;;i++)
		{
			if(5*i-5 >= y) break;
		}
		printf("%.0lf\n",i);
	}
	return 0;
}