H, W, A, B = list(map(int, input().split()))



mod = 10 ** 9 + 7



# 階乗

fac = [1] * (H + W - 2)

# 逆元

inv = [1] * (H + W - 2)

for i in range(1, H + W - 2):

    fac[i] = (fac[i - 1] * i) % mod

    inv[i] = pow(fac[i], mod - 2, mod)





def f(x, y):

    res = fac[x + y] * inv[x] * inv[y]

    return res % mod





ans = 0

for x in range(B, W):

    ans += f(x, H - A - 1) * f(W - 1 - x, A - 1)

print((ans % mod))



H, W, A, B = list(map(int, input().split()))



mod = 10**9 + 7

N = H + W - 2



# 階乗

fac = [1] * N

for i in range(1, N):

    fac[i] = (fac[i - 1] * i) % mod



# 逆元

inv = [1] * N

inv[N - 1] = pow(fac[N - 1], mod - 2, mod)

for i in range(N - 1, 0, -1):

    inv[i - 1] = (inv[i] * i) % mod





def f(x, y):

    res = fac[x + y] * inv[x] * inv[y]

    return res % mod





ans = 0

for x in range(B, W):

    ans += f(x, H - A - 1) * f(W - 1 - x, A - 1)

print((ans % mod))

H, W, A, B = list(map(int, input().split()))
mod = 10**9 + 7
# 階乗
fac = [1] * (H + W - 2)
# 逆元
inv = [1] * (H + W - 2)
for i in range(1, H + W - 2):
    fac[i] = (fac[i - 1] * i) % mod
    inv[i] = pow(fac[i], mod - 2, mod)


def f(x, y):
    res = fac[x + y] * inv[x] * inv[y]
    return res % mod


ans = 0
for x in range(B, W):
    ans += f(x, H - A - 1) * f(W - 1 - x, A - 1)
print((ans % mod))

H, W, A, B = list(map(int, input().split()))
mod = 10**9 + 7
N = H + W - 2
# 階乗
fac = [1] * N
for i in range(1, N):
    fac[i] = (fac[i - 1] * i) % mod
# 逆元
inv = [1] * N
inv[N - 1] = pow(fac[N - 1], mod - 2, mod)
for i in range(N - 1, 0, -1):
    inv[i - 1] = (inv[i] * i) % mod


def f(x, y):
    res = fac[x + y] * inv[x] * inv[y]
    return res % mod


ans = 0
for x in range(B, W):
    ans += f(x, H - A - 1) * f(W - 1 - x, A - 1)
print((ans % mod))

+N = H + W - 2 -fac = [1] * (H + W - 2) +fac = [1] * N +for i in range(1, N): +    fac[i] = (fac[i - 1] * i) % mod -inv = [1] * (H + W - 2) -for i in range(1, H + W - 2): -    fac[i] = (fac[i - 1] * i) % mod -    inv[i] = pow(fac[i], mod - 2, mod) +inv = [1] * N +inv[N - 1] = pow(fac[N - 1], mod - 2, mod) +for i in range(N - 1, 0, -1): +    inv[i - 1] = (inv[i] * i) % mod