x1,y1,x2,y2,x3,y3=map(int,input().split())

def X(a,b,c):
  ax,ay=a
  bx,by=b
  cx,cy=c
  return (ax-cx)*(by-cy)-(ay-cy)*(bx-cx)

s=0

for dx1,dy1 in [(1,0),(-1,0),(0,1),(0,-1)]:
  for dx2,dy2 in [(1,0),(-1,0),(0,1),(0,-1)]:
    for dx3,dy3 in [(1,0),(-1,0),(0,1),(0,-1)]:
      s=max(s,abs(X((x1+dx1,y1+dy1),(x2+dx2,y2+dy2),(x3+dx3,y3+dy3))))

print(s/2)