def menseki_triangle(a,b,c):
    x1,y1 = a[0],a[1]
    x2,y2 = b[0],b[1]
    x3,y3 = c[0],c[1]

    return abs((x1-x3)*(y2-y3)-(x2-x3)*(y1-y3))/2

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

t = [[1,0],[-1,0],[0,1],[0,-1]]

ans = -1
for a,b in t:
    for c,d in t:
        for e,f in t:
            tmpans = menseki_triangle([x1+a,y1+b],[x2+c,y2+d],[x3+e,y3+f])
            ans = max(ans,tmpans)

print(ans)