H, W, A, B = list(map(int, open(0).read().split()))

MOD = 10**9+7



factorials = [1] * (H + W + 1)

inv_factorials = [1] * (H + W + 1)



for i in range(H + W):

    factorials[i+1] = factorials[i] * (i + 1) % MOD



inv_factorials = list([pow(n, -1, MOD) for n in factorials])



def modcomb(m, n, mod):

    return factorials[m] * inv_factorials[n] % MOD * inv_factorials[m - n] % MOD

 

total = modcomb(H + W - 2, W - 1, MOD)

 

for i in range(B):

    total -= modcomb(H - A - 1 + i, i, MOD) * modcomb(A - 1 + W - 1 - i, W - 1 - i, MOD) % MOD

    total %= MOD

 

print(total)
H, W, A, B = list(map(int, open(0).read().split()))

MOD = 10**9+7



factorials = [1] * (H + W + 1)

inv_factorials = [1] * (H + W + 1)



for i in range(H + W):

    factorials[i+1] = factorials[i] * (i + 1) % MOD



inv_factorials = list([pow(n, MOD - 2, MOD) for n in factorials])



def modcomb(m, n, mod):

    return factorials[m] * inv_factorials[n] % MOD * inv_factorials[m - n] % MOD

 

# total = modcomb(H + W - 2, W - 1, MOD)

total = 0

 

# for i in range(B):

for i in range(B, W):

    total += modcomb(H - A - 1 + i, i, MOD) * modcomb(A - 1 + W - 1 - i, W - 1 - i, MOD) % MOD

    total %= MOD

 

print(total)
H, W, A, B = list(map(int, open(0).read().split()))
MOD = 10**9 + 7
factorials = [1] * (H + W + 1)
inv_factorials = [1] * (H + W + 1)
for i in range(H + W):
    factorials[i + 1] = factorials[i] * (i + 1) % MOD
inv_factorials = list([pow(n, -1, MOD) for n in factorials])


def modcomb(m, n, mod):
    return factorials[m] * inv_factorials[n] % MOD * inv_factorials[m - n] % MOD


total = modcomb(H + W - 2, W - 1, MOD)
for i in range(B):
    total -= (
        modcomb(H - A - 1 + i, i, MOD)
        * modcomb(A - 1 + W - 1 - i, W - 1 - i, MOD)
        % MOD
    )
    total %= MOD
print(total)

H, W, A, B = list(map(int, open(0).read().split()))
MOD = 10**9 + 7
factorials = [1] * (H + W + 1)
inv_factorials = [1] * (H + W + 1)
for i in range(H + W):
    factorials[i + 1] = factorials[i] * (i + 1) % MOD
inv_factorials = list([pow(n, MOD - 2, MOD) for n in factorials])


def modcomb(m, n, mod):
    return factorials[m] * inv_factorials[n] % MOD * inv_factorials[m - n] % MOD


# total = modcomb(H + W - 2, W - 1, MOD)
total = 0
# for i in range(B):
for i in range(B, W):
    total += (
        modcomb(H - A - 1 + i, i, MOD)
        * modcomb(A - 1 + W - 1 - i, W - 1 - i, MOD)
        % MOD
    )
    total %= MOD
print(total)

-inv_factorials = list([pow(n, -1, MOD) for n in factorials]) +inv_factorials = list([pow(n, MOD - 2, MOD) for n in factorials]) -total = modcomb(H + W - 2, W - 1, MOD) -for i in range(B): -    total -= ( +# total = modcomb(H + W - 2, W - 1, MOD) +total = 0 +# for i in range(B): +for i in range(B, W): +    total += (