#include<stdio.h>
#define EPS 1e-9
double v;

int main(){
	double h;
	int ans;
	while( scanf("%lf",&v) != EOF )
	{
		h = (v*v)/19.6;
		ans = h/5.0;
		h -= ans*5.0;
		if( h > EPS )
			ans++;
		ans++;
		
		printf("%d\n",ans);
	}
	return 0;
}