bx, by, hx, hy = map(int, input().split()) a = [] b = [] for i in range(by + 1): a.append([0] * (bx + 1)) b.append([0] * (bx + 1))

b[0][0] = 1 for i in range(by + 1): for j in range(bx + 1): disY = abs(i - hy) disX = abs(j - hx) if disX == 1 and disY == 2: a[i][j] = -1 elif disY == 0 and disX == 0: a[i][j] = -1 elif disX == 2 and disY == 1: a[i][j] = -1

for i in range(1, by + 1): if a[i - 1][0] != -1 and a[i][0] != -1: b[i][0] = b[i - 1][0]

for j in range(1, bx + 1): if a[0][j] != -1 and a[0][j - 1] != -1: b[0][j] = b[0][j - 1]

for i in range(1, by + 1): for j in range(1, bx + 1): if a[i][j] != -1: b[i][j] = b[i - 1][j] + b[i][j-1] print(b[by][bx])