x1,y1,x2,y2,x3,y3=map(int,input().split())
ans=0
d=(1,0),(-1,0),(0,1),(0,-1)
for i in range(4):
	xi,yi=x1+d[i][0],y1+d[i][1]
	for j in range(4):
		xj,yj=x2+d[j][0],y2+d[j][1]
		for k in range(4):
			xk,yk=x3+d[k][0],y3+d[k][1]
			s=abs((xj-xi)*(yk-yi)-(xk-xi)*(yj-yi))
			ans=max(ans,s)
print(ans/2)