#208.py
tx,ty = input().split()
hx,hy = input().split()
tx,ty = int(tx),int(ty)
hx,hy = int(hx),int(hy)
x,y = 0,0
x_,y_ = 0,0
lx,ly = -1,-1
c = 0

while(1):
    lx = tx-x
    ly = ty-y
    if(lx+ly == 0):
        break
    c+=1
    if(lx == ly):
        x+=1
        y+=1
    if(lx > ly):
        x+=1
    if(lx < ly):
        y+=1
    if(hx == x)&(hy == y):
        if(x_ != x)&(y_ != y):
            if(tx <= ty):
                x-=1
            if(tx > ty):
                y-=1
        if(x_ == x):
            y+=1
        if(y_ == y):
            x+=1
    x_,y_ = x,y
print(c)