Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
import math as m

def main(**kwargs):
    mod = 10 ** 9 + 7
    r = repeatSquare(2, n, mod) - 1
    r -= m.factorial(n) * repeatSquare(m.factorial(n - a) * m.factorial(a), mod - 2, mod)
    r -= m.factorial(n) * repeatSquare(m.factorial(n - b) * m.factorial(b), mod - 2, mod)
    r = r % mod
    return r

def repeatSquare(n, p, m):
    if p == 0:
        return 1

    if p % 2 == 0:
        tmp = repeatSquare(n, p/2, m)
        return tmp * tmp % m

    return n * repeatSquare(n, p-1, m)

if __name__ == "__main__":
    cin = np.array(input().split(" ")).astype("int")
    n, a, b = cin

    cout = main(n=n, a=a, b=b)
    print(cout)

Fixed submission:
import numpy as np
import math as m

def main(**kwargs):
    mod = 10 ** 9 + 7
    r = repeatSquare(2, n, mod) - 1
    r -= factMod(n, n - a + 1, mod) * repeatSquare(factMod(a, 1, mod), mod - 2, mod)
    r -= factMod(n, n - b + 1, mod) * repeatSquare(factMod(b, 1, mod), mod - 2, mod)
    r %= mod
    return r

def repeatSquare(n, p, m):
    if p == 0:
        return 1

    if p % 2 == 0:
        tmp = repeatSquare(n, p/2, m) % m
        return tmp * tmp % m

    return n * repeatSquare(n, p-1, m) % m

def factMod(n, r, m):
    res = n

    while n > r:
        n -= 1
        res *= n
        res %= m

    return res

if __name__ == "__main__":
    
    cin = np.array(input().split(" ")).astype("int")
    n, a, b = cin

    cout = main(n=n, a=a, b=b)
    print(cout)

Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
import math as m

def main(**kwargs):
    mod = 10 ** 9 + 7
    r = int(repeatSquare(2, n, mod) - 1 - m.factorial(n) * repeatSquare(m.factorial(n-a) * m.factorial(a), mod - 2, mod) - m.factorial(n) * repeatSquare(m.factorial(n-b) * m.factorial(b), mod - 2, mod)) % mod
    return r

def repeatSquare(n, p, m):
    if p == 0:
        return 1

    if p % 2 == 0:
        tmp = repeatSquare(n, p/2, m)
        return tmp * tmp % m

    return n * repeatSquare(n, p-1, m)

if __name__ == "__main__":
    cin = np.array(input().split(" ")).astype("int")
    n, a, b = cin

    cout = main(n=n, a=a, b=b)
    print(cout)

Fixed submission:
import numpy as np
import math as m

def main(**kwargs):
    mod = 10 ** 9 + 7
    r = repeatSquare(2, n, mod) - 1
    r -= factMod(n, n - a + 1, mod) * repeatSquare(factMod(a, 1, mod), mod - 2, mod)
    r -= factMod(n, n - b + 1, mod) * repeatSquare(factMod(b, 1, mod), mod - 2, mod)
    r %= mod
    return r

def repeatSquare(n, p, m):
    if p == 0:
        return 1

    if p % 2 == 0:
        tmp = repeatSquare(n, p/2, m) % m
        return tmp * tmp % m

    return n * repeatSquare(n, p-1, m) % m

def factMod(n, r, m):
    res = n

    while n > r:
        n -= 1
        res *= n
        res %= m

    return res

if __name__ == "__main__":
    
    cin = np.array(input().split(" ")).astype("int")
    n, a, b = cin

    cout = main(n=n, a=a, b=b)
    print(cout)

Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
import math as m

def main(**kwargs):
    mod = 10 ** 9 + 7
    facts = [m.factorial(i) % mod for i in range(n+1)]
    r = 0

    for i in range(1, n+1):
        if i != a and i != b:
            r += int((facts[n] / facts[n-i] / facts[i]))

    r %= mod
    return r

if __name__ == "__main__":
    cin = np.array(input().split(" ")).astype("int")
    n, a, b = cin

    cout = main(n=n, a=a, b=b)
    print(cout)

Fixed submission:
import numpy as np
import math as m

def main(**kwargs):
    mod = 10 ** 9 + 7
    r = repeatSquare(2, n, mod) - 1
    r -= factMod(n, n - a + 1, mod) * repeatSquare(factMod(a, 1, mod), mod - 2, mod)
    r -= factMod(n, n - b + 1, mod) * repeatSquare(factMod(b, 1, mod), mod - 2, mod)
    r %= mod
    return r

def repeatSquare(n, p, m):
    if p == 0:
        return 1

    if p % 2 == 0:
        tmp = repeatSquare(n, p/2, m) % m
        return tmp * tmp % m

    return n * repeatSquare(n, p-1, m) % m

def factMod(n, r, m):
    res = n

    while n > r:
        n -= 1
        res *= n
        res %= m

    return res

if __name__ == "__main__":
    
    cin = np.array(input().split(" ")).astype("int")
    n, a, b = cin

    cout = main(n=n, a=a, b=b)
    print(cout)

Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
import math as m

def main(**kwargs):
    mod = 10 ** 9 + 7
    facts = [m.factorial(i) % mod for i in range(n+1)]
 
    r = int((2 ** n - 1 - facts[n] / facts[n-a] / facts[a] - facts[n] / facts[n-b] / facts[b]) % mod)
    return r

if __name__ == "__main__":
    cin = np.array(input().split(" ")).astype("int")
    n, a, b = cin

    cout = main(n=n, a=a, b=b)
    print(cout)

Fixed submission:
import numpy as np
import math as m

def main(**kwargs):
    mod = 10 ** 9 + 7
    r = repeatSquare(2, n, mod) - 1
    r -= factMod(n, n - a + 1, mod) * repeatSquare(factMod(a, 1, mod), mod - 2, mod)
    r -= factMod(n, n - b + 1, mod) * repeatSquare(factMod(b, 1, mod), mod - 2, mod)
    r %= mod
    return r

def repeatSquare(n, p, m):
    if p == 0:
        return 1

    if p % 2 == 0:
        tmp = repeatSquare(n, p/2, m) % m
        return tmp * tmp % m

    return n * repeatSquare(n, p-1, m) % m

def factMod(n, r, m):
    res = n

    while n > r:
        n -= 1
        res *= n
        res %= m

    return res

if __name__ == "__main__":
    
    cin = np.array(input().split(" ")).astype("int")
    n, a, b = cin

    cout = main(n=n, a=a, b=b)
    print(cout)