Buggy python submission (verdict: Time Limit Exceeded):
#!usr/bin/env python3
from collections import defaultdict
from heapq import heappush, heappop
import sys
import math
import bisect
import random
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS(): return list(map(list, sys.stdin.readline().split()))
def S(): return list(sys.stdin.readline())[:-1]
def IR(n): return [I() for i in range(n)]
def LIR(n): return [LI() for i in range(n)]
def SR(n): return [S() for i in range(n)]
def LSR(n): return [LS() for i in range(n)]
mod = 1000000007


#A
"""
def check(n):
    n = list(map(int,list(str(n))))
    s = 0
    for i in n:
        s += f[i]
    return s == 0
n,k = LI()
d = LI()
f = [0 for i in range(10)]
for i in d:
    f[i] = 1
while 1:
    if check(n):
        print(n)
        quit()
    n += 1
"""
#B
def f(x,y):
    return fact[x-1+h-y]*fact[y-1+w-x]*inv_fact[x-1]*inv_fact[y-1]*inv_fact[w-x]*inv_fact[h-y]%mod
h,w,a,b = LI()
fact = [1]
for i in range(h+w):
    fact.append(fact[-1]*(i+1)%mod)
inv_fact = [pow(fact[-1],mod-2,mod)]
for i in range(h+w):
    inv_fact.insert(0,inv_fact[0]*(h+w-i)%mod)
ans = 0
for i in range(1,min(w-b,h-a)+1):
    ans += f(b+i,a+i)
    ans %= mod
print(ans)
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Fixed submission:
#!usr/bin/env python3
from collections import defaultdict
from heapq import heappush, heappop
import sys
import math
import bisect
import random
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS(): return list(map(list, sys.stdin.readline().split()))
def S(): return list(sys.stdin.readline())[:-1]
def IR(n): return [I() for i in range(n)]
def LIR(n): return [LI() for i in range(n)]
def SR(n): return [S() for i in range(n)]
def LSR(n): return [LS() for i in range(n)]
mod = 1000000007


#A
"""
def check(n):
    n = list(map(int,list(str(n))))
    s = 0
    for i in n:
        s += f[i]
    return s == 0
n,k = LI()
d = LI()
f = [0 for i in range(10)]
for i in d:
    f[i] = 1
while 1:
    if check(n):
        print(n)
        quit()
    n += 1
"""
#B
h,w,a,b = LI()
ans = 0
k = 1
inv = [pow(i,mod-2,mod) for i in range(h+w+1)]
x = b+1
y = a+1
for i in range(min(x-1,h-y)):
    k *= (x-1+h-y-i)*inv[i+1]%mod
    k %= mod
for i in range(min(y-1,w-x)):
    k *= (y-1+w-x-i)*inv[i+1]%mod
    k %= mod
for i in range(1,min(w-b,h-a)+1):
    ans += k
    ans %= mod
    k *= (h-y)*(w-x)*inv[x]*inv[y]%mod
    k %= mod
    x += 1
    y += 1
print(ans)
#C

#D

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#T

Buggy python submission (verdict: Time Limit Exceeded):
#!usr/bin/env python3
from collections import defaultdict
from heapq import heappush, heappop
import sys
import math
import bisect
import random
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS(): return list(map(list, sys.stdin.readline().split()))
def S(): return list(sys.stdin.readline())[:-1]
def IR(n): return [I() for i in range(n)]
def LIR(n): return [LI() for i in range(n)]
def SR(n): return [S() for i in range(n)]
def LSR(n): return [LS() for i in range(n)]
mod = 1000000007


#A
"""
def check(n):
    n = list(map(int,list(str(n))))
    s = 0
    for i in n:
        s += f[i]
    return s == 0
n,k = LI()
d = LI()
f = [0 for i in range(10)]
for i in d:
    f[i] = 1
while 1:
    if check(n):
        print(n)
        quit()
    n += 1
"""
#B
def f(x,y):
    return fact[x-1+h-y]*fact[y-1+w-x]*inv_fact[x-1]*inv_fact[y-1]*inv_fact[w-x]*inv_fact[h-y]%mod
h,w,a,b = LI()
fact = [1]
for i in range(h+w):
    fact.append(fact[-1]*(i+1)%mod)
inv_fact = [pow(fact[-1],mod-2,mod)]
for i in range(h+w):
    inv_fact.insert(0,inv_fact[0]*(h+w-i)%mod)
ans = 0
for i in range(1,min(w-b,h-a)+1):
    ans += f(b+i,a+i)
    ans %= mod
print(ans)
#C

#D

#E

#F

#G

#H

#I

#J

#K

#L

#M

#N

#O

#P

#Q

#R

#S

#T


Fixed submission:
#!usr/bin/env python3
from collections import defaultdict
from heapq import heappush, heappop
import sys
import math
import bisect
import random
def LI(): return list(map(int, sys.stdin.readline().split()))
def I(): return int(sys.stdin.readline())
def LS(): return list(map(list, sys.stdin.readline().split()))
def S(): return list(sys.stdin.readline())[:-1]
def IR(n): return [I() for i in range(n)]
def LIR(n): return [LI() for i in range(n)]
def SR(n): return [S() for i in range(n)]
def LSR(n): return [LS() for i in range(n)]
mod = 1000000007


#A
"""
def check(n):
    n = list(map(int,list(str(n))))
    s = 0
    for i in n:
        s += f[i]
    return s == 0
n,k = LI()
d = LI()
f = [0 for i in range(10)]
for i in d:
    f[i] = 1
while 1:
    if check(n):
        print(n)
        quit()
    n += 1
"""
#B
h,w,a,b = LI()
ans = 0
k = 1
inv = [pow(i,mod-2,mod) for i in range(h+w+1)]
x = b+1
y = a+1
for i in range(min(x-1,h-y)):
    k *= (x-1+h-y-i)*inv[i+1]%mod
    k %= mod
for i in range(min(y-1,w-x)):
    k *= (y-1+w-x-i)*inv[i+1]%mod
    k %= mod
for i in range(1,min(w-b,h-a)+1):
    ans += k
    ans %= mod
    k *= (h-y)*(w-x)*inv[x]*inv[y]%mod
    k %= mod
    x += 1
    y += 1
print(ans)
#C

#D

#E

#F

#G

#H

#I

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#T