import math

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

p = 10 ** 9 + 7

F = [1 for i in range(H + W + 1)]

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

  F[i] = F[i - 1] * i % p

def fac(a, b):

  a = F[a + b] * pow(F[a], p - 2, p) * pow(F[b], p - 2, p)

  return a % p

ans = 0

for h in range(H - A):

  ans += fac(h, B - 1) * fac(H - h - 1, W - B - 1) % p

print((ans % p))
H, W, A, B = list(map(int, input().split()))

p = 10 ** 9 + 7

F = [1 for i in range(H + W + 1)]

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

  F[i] = F[i - 1] * i % p

Fi = [pow(f, p - 2, p) for f in F]

def fac(a, b):

  a = F[a + b] * Fi[a] * Fi[b]

  return a % p

if H - A < B:

  ans = 0

  for h in range(H - A):

    ans += fac(h, B - 1) * fac(H - h - 1, W - B - 1) % p

else:

  ans = fac(H - 1, W- 1)

  for w in range(B):

    ans -= fac(H - A - 1, w) * fac(A - 1, W - w - 1) % p

print((ans % p))
import math

H, W, A, B = list(map(int, input().split()))
p = 10**9 + 7
F = [1 for i in range(H + W + 1)]
for i in range(1, H + W + 1):
    F[i] = F[i - 1] * i % p


def fac(a, b):
    a = F[a + b] * pow(F[a], p - 2, p) * pow(F[b], p - 2, p)
    return a % p


ans = 0
for h in range(H - A):
    ans += fac(h, B - 1) * fac(H - h - 1, W - B - 1) % p
print((ans % p))

H, W, A, B = list(map(int, input().split()))
p = 10**9 + 7
F = [1 for i in range(H + W + 1)]
for i in range(1, H + W + 1):
    F[i] = F[i - 1] * i % p
Fi = [pow(f, p - 2, p) for f in F]


def fac(a, b):
    a = F[a + b] * Fi[a] * Fi[b]
    return a % p


if H - A < B:
    ans = 0
    for h in range(H - A):
        ans += fac(h, B - 1) * fac(H - h - 1, W - B - 1) % p
else:
    ans = fac(H - 1, W - 1)
    for w in range(B):
        ans -= fac(H - A - 1, w) * fac(A - 1, W - w - 1) % p
print((ans % p))

-import math - +Fi = [pow(f, p - 2, p) for f in F] -    a = F[a + b] * pow(F[a], p - 2, p) * pow(F[b], p - 2, p) +    a = F[a + b] * Fi[a] * Fi[b] -ans = 0 -for h in range(H - A): -    ans += fac(h, B - 1) * fac(H - h - 1, W - B - 1) % p +if H - A < B: +    ans = 0 +    for h in range(H - A): +        ans += fac(h, B - 1) * fac(H - h - 1, W - B - 1) % p +else: +    ans = fac(H - 1, W - 1) +    for w in range(B): +        ans -= fac(H - A - 1, w) * fac(A - 1, W - w - 1) % p