N = int(input())
M = int(input())
x = int(input())
y = int(input())

if x>y and N>M:
    x0=N
    y0=M
elif x<y and N>M:
    x0=M
    y0=N
elif x<y and N<M:
    x0=N
    y0=M
else:
    x0=M
    y0=N

x1=abs(x0-x)
y1=abs(y0-y)

if x == N or y == N:
    print(0)
elif y == min(N,M,x,y) and abs(y0-y) > min(x1,y1,x,y):
    print(y)
elif x == min(N,M,x,y) and abs(x0-x) > min(x1,y1,x,y):
    print(x)
else:
    print(min(x1,y1,x,y))