Buggy python submission (verdict: Time Limit Exceeded):
r1,c1,r2,c2=map(int,input().split())
MOD=10**9+7

from scipy.special import comb

def comb_mod(n,k):
  return comb(n,k,exact=True)%MOD

ans=comb_mod(r2+c2+2,r2+1)+comb_mod(r1+c1,r1)-comb_mod(c1+r2+1,c1)-comb_mod(c2+r1+1,r1)
ans%=MOD
print(ans)


Fixed submission:
r1,c1,r2,c2=map(int,input().split())

mod = 10**9+7
MAX_N = 3*10**6

fact = [1]
fact_inv = [0]*(MAX_N+4)
for i in range(MAX_N+3):
    fact.append(fact[-1]*(i+1)%mod)

fact_inv[-1] = pow(fact[-1],mod-2,mod)
for i in range(MAX_N+2,-1,-1):
    fact_inv[i] = fact_inv[i+1]*(i+1)%mod

def comb(n,k,mod):
    if n<k:return 0
    return fact[n] * fact_inv[k] % mod * fact_inv[n-k] %mod

ans=0
ans+=comb(c1+r1,r1,mod)
ans%=mod
ans-=comb(c1+r2+1,r2+1,mod)
ans%=mod
ans-=comb(c2+r1+1,r1,mod)
ans%=mod
ans+=comb(c2+r2+2,r2+1,mod)
ans%=mod

print(ans)

Buggy python submission (verdict: Runtime Error):
r1,c1,r2,c2=map(int,input().split())

mod = 10**9+7
MAX_N = 10**6

fact = [1]
fact_inv = [0]*(MAX_N+4)
for i in range(MAX_N+3):
    fact.append(fact[-1]*(i+1)%mod)

fact_inv[-1] = pow(fact[-1],mod-2,mod)
for i in range(MAX_N+2,-1,-1):
    fact_inv[i] = fact_inv[i+1]*(i+1)%mod

def comb(n,k,mod):
    if n<k:return 0
    return fact[n] * fact_inv[k] % mod * fact_inv[n-k] %mod

ans=0
ans+=comb(c1+r1,r1,mod)
ans%=mod
ans-=comb(c1+r2+1,r2+1,mod)
ans%=mod
ans-=comb(c2+r1+1,r1,mod)
ans%=mod
ans+=comb(c2+r2+2,r2+1,mod)
ans%=mod

print(ans)


Fixed submission:
r1,c1,r2,c2=map(int,input().split())

mod = 10**9+7
MAX_N = 3*10**6

fact = [1]
fact_inv = [0]*(MAX_N+4)
for i in range(MAX_N+3):
    fact.append(fact[-1]*(i+1)%mod)

fact_inv[-1] = pow(fact[-1],mod-2,mod)
for i in range(MAX_N+2,-1,-1):
    fact_inv[i] = fact_inv[i+1]*(i+1)%mod

def comb(n,k,mod):
    if n<k:return 0
    return fact[n] * fact_inv[k] % mod * fact_inv[n-k] %mod

ans=0
ans+=comb(c1+r1,r1,mod)
ans%=mod
ans-=comb(c1+r2+1,r2+1,mod)
ans%=mod
ans-=comb(c2+r1+1,r1,mod)
ans%=mod
ans+=comb(c2+r2+2,r2+1,mod)
ans%=mod

print(ans)

Buggy python submission (verdict: Runtime Error):
r1,c1,r2,c2=map(int,input().split())

mod = 10**9+7
MAX_N = 10**6

fact = [1]
fact_inv = [0]*(MAX_N+4)
for i in range(MAX_N+3):
    fact.append(fact[-1]*(i+1)%mod)

fact_inv[-1] = pow(fact[-1],mod-2,mod)
for i in range(MAX_N+2,-1,-1):
    fact_inv[i] = fact_inv[i+1]*(i+1)%mod

def comb(n,k,mod):
    return fact[n] * fact_inv[k] % mod * fact_inv[n-k] %mod

ans=0
ans+=comb(c1+r1,r1,mod)
ans%=mod
ans-=comb(c1+r2+1,r2+1,mod)
ans%=mod
ans-=comb(c2+r1+1,r1,mod)
ans%=mod
ans+=comb(c2+r2+2,r2+1,mod)
ans%=mod

print(ans)


Fixed submission:
r1,c1,r2,c2=map(int,input().split())

mod = 10**9+7
MAX_N = 3*10**6

fact = [1]
fact_inv = [0]*(MAX_N+4)
for i in range(MAX_N+3):
    fact.append(fact[-1]*(i+1)%mod)

fact_inv[-1] = pow(fact[-1],mod-2,mod)
for i in range(MAX_N+2,-1,-1):
    fact_inv[i] = fact_inv[i+1]*(i+1)%mod

def comb(n,k,mod):
    if n<k:return 0
    return fact[n] * fact_inv[k] % mod * fact_inv[n-k] %mod

ans=0
ans+=comb(c1+r1,r1,mod)
ans%=mod
ans-=comb(c1+r2+1,r2+1,mod)
ans%=mod
ans-=comb(c2+r1+1,r1,mod)
ans%=mod
ans+=comb(c2+r2+2,r2+1,mod)
ans%=mod

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
r1,c1,r2,c2=map(int,input().split())

from scipy.special import comb
MOD=10**9+7

ans=0
ans+=comb(c1+r1,r1,exact=True)
ans%=MOD
ans-=comb(c1+r2+1,r2+1,exact=True)
ans%=MOD
ans-=comb(c2+r1+1,r1,exact=True)
ans%=MOD
ans+=comb(c2+r2+2,r2+1,exact=True)
ans%=MOD

print(ans)

Fixed submission:
r1,c1,r2,c2=map(int,input().split())

mod = 10**9+7
MAX_N = 3*10**6

fact = [1]
fact_inv = [0]*(MAX_N+4)
for i in range(MAX_N+3):
    fact.append(fact[-1]*(i+1)%mod)

fact_inv[-1] = pow(fact[-1],mod-2,mod)
for i in range(MAX_N+2,-1,-1):
    fact_inv[i] = fact_inv[i+1]*(i+1)%mod

def comb(n,k,mod):
    if n<k:return 0
    return fact[n] * fact_inv[k] % mod * fact_inv[n-k] %mod

ans=0
ans+=comb(c1+r1,r1,mod)
ans%=mod
ans-=comb(c1+r2+1,r2+1,mod)
ans%=mod
ans-=comb(c2+r1+1,r1,mod)
ans%=mod
ans+=comb(c2+r2+2,r2+1,mod)
ans%=mod

print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
r1,c1,r2,c2=map(int,input().split())

#O(10**12) orz

from scipy.misc import comb
mod=10**9+7
tret=0
for i in range(r1,r2+1):
    for j in range(c1,c2+1):
        # print(i,j)
        tret+=comb(i+j,i,exact=True)
        tret%=mod
        
print(tret)
        

Fixed submission:
r1,c1,r2,c2=map(int,input().split())

mod = 10**9+7
MAX_N = 3*10**6

fact = [1]
fact_inv = [0]*(MAX_N+4)
for i in range(MAX_N+3):
    fact.append(fact[-1]*(i+1)%mod)

fact_inv[-1] = pow(fact[-1],mod-2,mod)
for i in range(MAX_N+2,-1,-1):
    fact_inv[i] = fact_inv[i+1]*(i+1)%mod

def comb(n,k,mod):
    if n<k:return 0
    return fact[n] * fact_inv[k] % mod * fact_inv[n-k] %mod

ans=0
ans+=comb(c1+r1,r1,mod)
ans%=mod
ans-=comb(c1+r2+1,r2+1,mod)
ans%=mod
ans-=comb(c2+r1+1,r1,mod)
ans%=mod
ans+=comb(c2+r2+2,r2+1,mod)
ans%=mod

print(ans)

Buggy python submission (verdict: Runtime Error):
r1,c1,r2,c2=map(int,input().split())

#O(10**12) orz

from scipy.misc import comb
mod=10**9+7
tret=0
for i in range(r1,r2+1):
    for j in range(c1,c2+1):
        # print(i,j)
        tret+=comb(i+j,i,exact=True)
        tret%=mod
        
print(tret)
        

Fixed submission:
r1,c1,r2,c2=map(int,input().split())

mod = 10**9+7
MAX_N = 3*10**6

fact = [1]
fact_inv = [0]*(MAX_N+4)
for i in range(MAX_N+3):
    fact.append(fact[-1]*(i+1)%mod)

fact_inv[-1] = pow(fact[-1],mod-2,mod)
for i in range(MAX_N+2,-1,-1):
    fact_inv[i] = fact_inv[i+1]*(i+1)%mod

def comb(n,k,mod):
    if n<k:return 0
    return fact[n] * fact_inv[k] % mod * fact_inv[n-k] %mod

ans=0
ans+=comb(c1+r1,r1,mod)
ans%=mod
ans-=comb(c1+r2+1,r2+1,mod)
ans%=mod
ans-=comb(c2+r1+1,r1,mod)
ans%=mod
ans+=comb(c2+r2+2,r2+1,mod)
ans%=mod

print(ans)