Buggy python submission (verdict: Runtime Error):
def nCr(n, r):
    return ((((fact[n]*finv[n-r])%mod)*finv[r])%mod)

def powmod(a, n, m):
    if n == 0:
        return 1
    elif n == 1:
        return (a % m)
    elif n%2 == 0:
        s = powmod(a, int(n/2), m)
        temp = (s * s) % m
        return temp
    else:
        s = powmod(a, int(n/2), m)
        temp = ((s * s) * a) % m
        return temp

mod = 10**9 + 7
inv = mod - 2
maxn = high + width - 2
fact = [0] * (maxn+1)
finv = [0] * (maxn+1)
fact[0] = fact[1] = 1
finv[0] = finv[1] = 1

# 階乗を求める
for i in range(2, maxn+1):
    fact[i] = (fact[i-1] * i) % mod

# 階乗の逆元を求める
for i in range(2, maxn+1):
    finv[i] = powmod(fact[i], inv, mod)

route = 0
for i in range(1, high-y+1):
        route += (nCr(x+i-2, i-1) * nCr(width+high-x-1-i, high-i)) % mod
        route = route % mod
print(int(route))

Fixed submission:
high, width, y, x = map(int, input().split())

def nCr(n, r):
    return ((((fact[n]*finv[n-r])%mod)*finv[r])%mod)

mod = 10**9 + 7
inv = mod - 2
maxn = high + width - 2
fact = [0] * (maxn+1)
finv = [0] * (maxn+1)
fact[0] = fact[1] = 1
finv[0] = finv[1] = 1

# 階乗を求める
for i in range(2, maxn+1):
    fact[i] = (fact[i-1] * i) % mod

# 階乗の逆元を求める
for i in range(2, maxn+1):
    finv[i] = pow(fact[i], inv, mod)

route = 0
for i in range(1, high-y+1):
        route += (nCr(x+i-2, i-1) * nCr(width+high-x-1-i, high-i)) % mod
        route = route % mod
print(int(route))

Buggy python submission (verdict: Time Limit Exceeded):
high, width, y, x = map(int, input().split())

def nCr(n, r):
    return ((((fact[n]*finv[n-r])%mod)*finv[r])%mod)

def powmod(a, n, m):
    if n == 0:
        return 1
    elif n == 1:
        return (a % m)
    elif n%2 == 0:
        s = powmod(a, int(n/2), m)
        temp = (s * s) % m
        return temp
    else:
        s = powmod(a, int(n/2), m)
        temp = (((s * s) % m) * a) % m
        return temp

mod = 10**9 + 7
inv = mod - 2
maxn = high + width - 2
fact = [0] * (maxn+1)
finv = [0] * (maxn+1)
fact[0] = fact[1] = 1
finv[0] = finv[1] = 1

# 階乗を求める
for i in range(2, maxn+1):
    fact[i] = (fact[i-1] * i) % mod

# 階乗の逆元を求める
for i in range(2, maxn+1):
    finv[i] = powmod(fact[i], inv, mod)

route = 0
for i in range(1, high-y+1):
        route += (nCr(x+i-2, i-1) * nCr(width+high-x-1-i, high-i)) % mod
        route = route % mod
print(int(route))

Fixed submission:
high, width, y, x = map(int, input().split())

def nCr(n, r):
    return ((((fact[n]*finv[n-r])%mod)*finv[r])%mod)

mod = 10**9 + 7
inv = mod - 2
maxn = high + width - 2
fact = [0] * (maxn+1)
finv = [0] * (maxn+1)
fact[0] = fact[1] = 1
finv[0] = finv[1] = 1

# 階乗を求める
for i in range(2, maxn+1):
    fact[i] = (fact[i-1] * i) % mod

# 階乗の逆元を求める
for i in range(2, maxn+1):
    finv[i] = pow(fact[i], inv, mod)

route = 0
for i in range(1, high-y+1):
        route += (nCr(x+i-2, i-1) * nCr(width+high-x-1-i, high-i)) % mod
        route = route % mod
print(int(route))

Buggy python submission (verdict: Runtime Error):
high, width, y, x = map(int, input().split())

def nCr(n, r):
    return ((((fact[n]*finv[n-r])%mod)*finv[r])%mod)
def powmod(a, n, m):
    if n == 0:
        return 1
    elif n == 1:
        return a
    if n%2 == 0:
        temp = (powmod(a, n/2, m) ** 2) % m
        return temp
    else:
        temp = (((powmod(a, n/2, m) ** 2) % m) * a) % m
        return temp

mod = 10**9 + 7
inv = mod - 2
maxn = high + width - 2
fact = [0] * (maxn+1)
finv = [0] * (maxn+1)
fact[0] = fact[1] = 1
finv[0] = finv[1] = 1

# 階乗を求める
for i in range(2, maxn+1):
    fact[i] = (fact[i-1] * i) % mod

# 階乗の逆元を求める
for i in range(2, maxn+1):
    finv[i] = powmod(fact[i], inv, mod)

route = 0
for i in range(1, high-y+1):
        route += (nCr(x+i-2, i-1) * nCr(width+high-x-1-i, high-i)) % mod
        route = route % mod
print(int(route))

Fixed submission:
high, width, y, x = map(int, input().split())

def nCr(n, r):
    return ((((fact[n]*finv[n-r])%mod)*finv[r])%mod)

mod = 10**9 + 7
inv = mod - 2
maxn = high + width - 2
fact = [0] * (maxn+1)
finv = [0] * (maxn+1)
fact[0] = fact[1] = 1
finv[0] = finv[1] = 1

# 階乗を求める
for i in range(2, maxn+1):
    fact[i] = (fact[i-1] * i) % mod

# 階乗の逆元を求める
for i in range(2, maxn+1):
    finv[i] = pow(fact[i], inv, mod)

route = 0
for i in range(1, high-y+1):
        route += (nCr(x+i-2, i-1) * nCr(width+high-x-1-i, high-i)) % mod
        route = route % mod
print(int(route))

Buggy python submission (verdict: Runtime Error):
high, width, y, x = map(int, input().split())

import math
route = 0
for i in range(1,high-y+1):
    if i != high-y:
        route += ((math.factorial(x+i-1)/(math.factorial(x)*math.factorial(i-1)))%(10**9+7))*((math.factorial(width-x-2+high-i)/(math.factorial(width-x-2)*math.factorial(high-i))))%(10**9+7)
    else:
        route += ((math.factorial(x+i-1)/(math.factorial(x)*math.factorial(i-1)))%(10**9+7))*((math.factorial(width-x-1+high-i)/(math.factorial(width-x-1)*math.factorial(high-i))))%(10**9+7)
print(int(route))

Fixed submission:
high, width, y, x = map(int, input().split())

def nCr(n, r):
    return ((((fact[n]*finv[n-r])%mod)*finv[r])%mod)

mod = 10**9 + 7
inv = mod - 2
maxn = high + width - 2
fact = [0] * (maxn+1)
finv = [0] * (maxn+1)
fact[0] = fact[1] = 1
finv[0] = finv[1] = 1

# 階乗を求める
for i in range(2, maxn+1):
    fact[i] = (fact[i-1] * i) % mod

# 階乗の逆元を求める
for i in range(2, maxn+1):
    finv[i] = pow(fact[i], inv, mod)

route = 0
for i in range(1, high-y+1):
        route += (nCr(x+i-2, i-1) * nCr(width+high-x-1-i, high-i)) % mod
        route = route % mod
print(int(route))