#include<stdio.h>

int main(void)
{
	double v,t,y;
	int n=1,h=0;
	while(scanf("%lf",&v)!=EOF)
	{
		t = v / 9.8;
		y = 4.9 * t*t;
		while(h<y)
		{
			n++;
			h=5*n-5;
		}
		printf("%d\n",n);
		n=1;
		h=0;
	}
	return 0;
}