X1,Y1,X2,Y2,X3,Y3=map(int,input().split())
ans=0
for x1,y1 in ((X1+1,Y1),(X1-1,Y1),(X1,Y1+1),(X1,Y1-1)):
    for x2,y2 in ((X2+1,Y2),(X2-1,Y2),(X2,Y2+1),(X2,Y2-1)):
        for x3,y3 in ((X3+1,Y3),(X3-1,Y3),(X3,Y3+1),(X3,Y3-1)):
            ans=max(ans,abs((x2-x1)*(y3-y1)-(x3-x1)*(y2-y1))/2)
print(ans)