Buggy python submission (verdict: Runtime Error):
import math 
  
# Function to find modulo inverse of b. It returns  
# -1 when inverse doesn't  
# modInverse works for prime m 
def modInverse(b,m): 
    g = math.gcd(b, m)  
    if (g != 1): 
        # print("Inverse doesn't exist")  
        return -1
    else:  
        # If b and m are relatively prime,  
        # then modulo inverse is b^(m-2) mode m  
        return pow(b, m - 2, m) 
  
  
# Function to compute a/b under modulo m  
def modDivide(a,b,m): 
    a = a % m 
    inv = modInverse(b,m) 
    if(inv == -1): 
        print("Division not defined") 
    else: 
        return (inv*a) % m

MOD = (10 ** 9) + 7
H, W, A, B = list(map(int, input().split(' ')))

DP = []
j = 1
for i in range(1,200002):
    j *= i
    j %= MOD
    DP.append(j)

# print(DP)
def factorial(i):
    if (i == 0):
        return 1
    global DP
    # print(i)
    # print(i, DP[i-1])
    # print(DP[i-1])
    return DP[i-1]

def move2(H, W, A, B):
    numPaths = 0
    h = H-A
    w = W-(W-B)+1
    a = A+1
    pttp = 0
    for b in range(w, W+1):
        # print(h, b, a, W-b+1)
        ttp = (factorial(h+b-2)*modInverse((factorial(h-1)*factorial(b-1))% MOD, MOD)) % MOD
        tpttp = ttp
        ttp -= pttp
        pttp = tpttp
        btp = (factorial(a+(W-b+1)-2)*modInverse((factorial(a-1)*factorial(W-b))% MOD, MOD)) % MOD
        # btp = factorial(a+(W-b+1)-2)//(factorial(a-1)*factorial(W-b))
        numPaths += ttp*btp
    return numPaths

ways = move2(H, W, A, B)
print(ways % (10**9 + 7))

Fixed submission:

# Function to find modulo inverse of b. It returns  
# -1 when inverse doesn't  
# modInverse works for prime m 
def gcd(b, m):
  if b == 0:
    return m
  return gcd(m%b, b)

def modInverse(b,m): 
    g = gcd(b, m) 
    if (g != 1): 
        # print("Inverse doesn't exist")  
        return -1
    else:  
        # If b and m are relatively prime,  
        # then modulo inverse is b^(m-2) mode m  
        return pow(b, m - 2, m) 
  
  
# Function to compute a/b under modulo m  
def modDivide(a,b,m): 
    a = a % m 
    inv = modInverse(b,m) 
    if(inv == -1): 
        print("Division not defined") 
    else: 
        return (inv*a) % m

MOD = (10 ** 9) + 7
H, W, A, B = list(map(int, input().split(' ')))

DP = []
j = 1
for i in range(1,200002):
    j *= i
    j %= MOD
    DP.append(j)

# print(DP)
def factorial(i):
    if (i == 0):
        return 1
    global DP
    # print(i)
    # print(i, DP[i-1])
    # print(DP[i-1])
    return DP[i-1]

def move2(H, W, A, B):
    numPaths = 0
    h = H-A
    w = W-(W-B)+1
    a = A+1
    pttp = 0
    for b in range(w, W+1):
        # print(h, b, a, W-b+1)
        ttp = (factorial(h+b-2)*modInverse((factorial(h-1)*factorial(b-1))% MOD, MOD)) % MOD
        tpttp = ttp
        ttp -= pttp
        pttp = tpttp
        btp = (factorial(a+(W-b+1)-2)*modInverse((factorial(a-1)*factorial(W-b))% MOD, MOD)) % MOD
        # btp = factorial(a+(W-b+1)-2)//(factorial(a-1)*factorial(W-b))
        numPaths += ttp*btp
    return numPaths

ways = move2(H, W, A, B)
print(ways % (10**9 + 7))

Buggy python submission (verdict: Time Limit Exceeded):
H, W, A, B = list(map(int, input().split(' ')))
def move(i, j, H, W, A, B):
    grid = [[0 for i in range(W)] for j in range(H)]
    
    for i in range(H-A):
        grid[i][0] = 1
    for i in range(W):
        grid[0][i] = 1
    # print(grid)
    for i in range(1, H):
        for j in range(1, W):
            # print(grid)
            upper = 0
            try:
                upper = grid[i-1][j]
            except:
                pass
            left = 0
            try:
                left = grid[i][j-1]
            except:
                pass
            if (i >= (H-A) and j < B):
                continue
            else:
                grid[i][j] = upper + left
    return grid[H-1][W-1]
    

ways = move(1, 1, H, W, A, B)
print(ways % (10**9 + 7))

Fixed submission:

# Function to find modulo inverse of b. It returns  
# -1 when inverse doesn't  
# modInverse works for prime m 
def gcd(b, m):
  if b == 0:
    return m
  return gcd(m%b, b)

def modInverse(b,m): 
    g = gcd(b, m) 
    if (g != 1): 
        # print("Inverse doesn't exist")  
        return -1
    else:  
        # If b and m are relatively prime,  
        # then modulo inverse is b^(m-2) mode m  
        return pow(b, m - 2, m) 
  
  
# Function to compute a/b under modulo m  
def modDivide(a,b,m): 
    a = a % m 
    inv = modInverse(b,m) 
    if(inv == -1): 
        print("Division not defined") 
    else: 
        return (inv*a) % m

MOD = (10 ** 9) + 7
H, W, A, B = list(map(int, input().split(' ')))

DP = []
j = 1
for i in range(1,200002):
    j *= i
    j %= MOD
    DP.append(j)

# print(DP)
def factorial(i):
    if (i == 0):
        return 1
    global DP
    # print(i)
    # print(i, DP[i-1])
    # print(DP[i-1])
    return DP[i-1]

def move2(H, W, A, B):
    numPaths = 0
    h = H-A
    w = W-(W-B)+1
    a = A+1
    pttp = 0
    for b in range(w, W+1):
        # print(h, b, a, W-b+1)
        ttp = (factorial(h+b-2)*modInverse((factorial(h-1)*factorial(b-1))% MOD, MOD)) % MOD
        tpttp = ttp
        ttp -= pttp
        pttp = tpttp
        btp = (factorial(a+(W-b+1)-2)*modInverse((factorial(a-1)*factorial(W-b))% MOD, MOD)) % MOD
        # btp = factorial(a+(W-b+1)-2)//(factorial(a-1)*factorial(W-b))
        numPaths += ttp*btp
    return numPaths

ways = move2(H, W, A, B)
print(ways % (10**9 + 7))