Buggy python submission (verdict: Runtime Error):
MOD = 10**9+7
def inv_mod(a,p=MOD):
    def inv_mod_sub(a,p):
        if a == 1:
            return 1,0
        else:
            d,r = p//a,p%a
            x,y = inv_mod_sub(r,a)
            return y-d*x,x
    if p < 0: p = -p
    a %= p
    return inv_mod_sub(a,p)[0] % p

def comb_mod(n,k):
    if k < 0 or k > n:
        return 0
    else:
        return f_mod[n]*f_mod_inverse[k]*f_mod_inverse[n-k] % MOD

def f(a,b):
  return comb_mod(a+b,b)

r1,c1,r2,c2 = map(int,input().split())
f_mod=[1]*(2*10**6)
f_mod_inverse=[1]*(2*10**6)
for i in range(1,2*10**6):
  f_mod[i]=f_mod[i-1]*i%MOD
  f_mod_inverse[i]=f_mod_inverse[i-1]*inv_mod(i)%MOD
print((f(r2+1,c2+1)-f(r1,c2+1)-f(r2+1,c1)+f(r1,c1))%MOD)

Fixed submission:
MOD = 10**9+7
def inv_mod(a,p=MOD):
    def inv_mod_sub(a,p):
        if a == 1:
            return 1,0
        else:
            d,r = p//a,p%a
            x,y = inv_mod_sub(r,a)
            return y-d*x,x
    if p < 0: p = -p
    a %= p
    return inv_mod_sub(a,p)[0] % p

def comb_mod(n,k):
    if k < 0 or k > n:
        return 0
    else:
        return f_mod[n]*f_mod_inverse[k]*f_mod_inverse[n-k] % MOD

def f(a,b):
  return comb_mod(a+b,b)

r1,c1,r2,c2 = map(int,input().split())
f_mod=[1]*(3*10**6)
f_mod_inverse=[1]*(3*10**6)
for i in range(1,3*10**6):
  f_mod[i]=f_mod[i-1]*i%MOD
  f_mod_inverse[i]=f_mod_inverse[i-1]*inv_mod(i)%MOD
print((f(r2+1,c2+1)-f(r1,c2+1)-f(r2+1,c1)+f(r1,c1))%MOD)

Buggy python submission (verdict: Runtime Error):
MOD = 10**9+7
def inv_mod(a,p=MOD):
    def inv_mod_sub(a,p):
        if a == 1:
            return 1,0
        else:
            d,r = p//a,p%a
            x,y = inv_mod_sub(r,a)
            return y-d*x,x
    if p < 0: p = -p
    a %= p
    return inv_mod_sub(a,p)[0] % p

def comb_mod(n,k):
    if k < 0 or k > n:
        return 0
    else:
        return f_mod[n]*f_mod_inverse[k]*f_mod_inverse[n-k] % MOD

def f(a,b):
  return comb_mod(a+b,b)

r1,c1,r2,c2 = map(int,input().split())
f_mod=[1]*(2*10**6)
f_mod_inverse=[1]*(2*10**6)
for i in range(1,10**6):
  f_mod[i]=f_mod[i-1]*i%MOD
  f_mod_inverse[i]=f_mod_inverse[i-1]*inv_mod(i)%MOD
print((f(r2+1,c2+1)-f(r1,c2+1)-f(r2+1,c1)+f(r1,c1))%MOD)

Fixed submission:
MOD = 10**9+7
def inv_mod(a,p=MOD):
    def inv_mod_sub(a,p):
        if a == 1:
            return 1,0
        else:
            d,r = p//a,p%a
            x,y = inv_mod_sub(r,a)
            return y-d*x,x
    if p < 0: p = -p
    a %= p
    return inv_mod_sub(a,p)[0] % p

def comb_mod(n,k):
    if k < 0 or k > n:
        return 0
    else:
        return f_mod[n]*f_mod_inverse[k]*f_mod_inverse[n-k] % MOD

def f(a,b):
  return comb_mod(a+b,b)

r1,c1,r2,c2 = map(int,input().split())
f_mod=[1]*(3*10**6)
f_mod_inverse=[1]*(3*10**6)
for i in range(1,3*10**6):
  f_mod[i]=f_mod[i-1]*i%MOD
  f_mod_inverse[i]=f_mod_inverse[i-1]*inv_mod(i)%MOD
print((f(r2+1,c2+1)-f(r1,c2+1)-f(r2+1,c1)+f(r1,c1))%MOD)

Buggy python submission (verdict: Runtime Error):
MOD = 10**9+7
def inv_mod(a,p=MOD):
    def inv_mod_sub(a,p):
        if a == 1:
            return 1,0
        else:
            d,r = p//a,p%a
            x,y = inv_mod_sub(r,a)
            return y-d*x,x
    if p < 0: p = -p
    a %= p
    return inv_mod_sub(a,p)[0] % p

def comb_mod(n,k):
    if k < 0 or k > n:
        return 0
    else:
        return f_mod[n]*f_mod_inverse[k]*f_mod_inverse[n-k] % MOD

def f(a,b):
  return comb_mod(a+b,b)

r1,c1,r2,c2 = map(int,input().split())
f_mod=[1]*(10**6)
f_mod_inverse=[1]*(10**6)
for i in range(1,10**6):
  f_mod[i]=f_mod[i-1]*i%MOD
  f_mod_inverse[i]=f_mod_inverse[i-1]*inv_mod(i)%MOD
print((f(r2+1,c2+1)-f(r1,c2+1)-f(r2+1,c1)+f(r1,c1))%MOD)

Fixed submission:
MOD = 10**9+7
def inv_mod(a,p=MOD):
    def inv_mod_sub(a,p):
        if a == 1:
            return 1,0
        else:
            d,r = p//a,p%a
            x,y = inv_mod_sub(r,a)
            return y-d*x,x
    if p < 0: p = -p
    a %= p
    return inv_mod_sub(a,p)[0] % p

def comb_mod(n,k):
    if k < 0 or k > n:
        return 0
    else:
        return f_mod[n]*f_mod_inverse[k]*f_mod_inverse[n-k] % MOD

def f(a,b):
  return comb_mod(a+b,b)

r1,c1,r2,c2 = map(int,input().split())
f_mod=[1]*(3*10**6)
f_mod_inverse=[1]*(3*10**6)
for i in range(1,3*10**6):
  f_mod[i]=f_mod[i-1]*i%MOD
  f_mod_inverse[i]=f_mod_inverse[i-1]*inv_mod(i)%MOD
print((f(r2+1,c2+1)-f(r1,c2+1)-f(r2+1,c1)+f(r1,c1))%MOD)