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