Buggy python submission (verdict: Time Limit Exceeded):
# import itertools
# import math
# import sys
# sys.setrecursionlimit(500*500)
# import numpy as np
# import heapq
# from collections import deque

# N = int(input())
# S = input()
# n, *a = map(int, open(0))
n, a, b = map(int, input().split())
# A = list(map(int, input().split()))
# B = list(map(int, input().split()))
# tree = [[] for _ in range(N + 1)]
# B_C = [list(map(int,input().split())) for _ in range(M)]
# S = input()

# B_C = sorted(B_C, reverse=True, key=lambda x:x[1])
# all_cases = list(itertools.permutations(P))
# a = list(itertools.combinations_with_replacement(range(1, M + 1), N))
# itertools.product((0,1), repeat=n)

# A = np.array(A)
# cum_A = np.cumsum(A)
# cum_A = np.insert(cum_A, 0, 0)

# def dfs(tree, s):
#     for l in tree[s]:
#         if depth[l[0]] == -1:
#             depth[l[0]] = depth[s] + l[1]
#             dfs(tree, l[0])
# dfs(tree, 1)

# def factorization(n):
#     arr = []
#     temp = n
#     for i in range(2, int(-(-n**0.5//1))+1):
#         if temp%i==0:
#             cnt=0
#             while temp%i==0:
#                 cnt+=1
#                 temp //= i
#             arr.append([i, cnt])
#     if temp!=1:
#         arr.append([temp, 1])
#     if arr==[]:
#         arr.append([n, 1])
#     return arr

def comb(n, m, mod = 10 ** 9 + 7):
    numerator = 1
    for i in range(n - m + 1, n + 1):
        numerator = numerator * i % mod
    denominator = 1
    for i in range(1, m + 1):
        denominator = denominator * i % mod
    d_inv = pow(denominator, mod - 2, mod)
    return numerator * d_inv

cmb_n_a = comb(n, a)
cmb_n_b = comb(n, b)

print((2 ** n - 1 - cmb_n_a - cmb_n_b) % (10 ** 9 + 7))

Fixed submission:
# import itertools
# import math
# import sys
# sys.setrecursionlimit(500*500)
# import numpy as np
# import heapq
# from collections import deque

# N = int(input())
# S = input()
# n, *a = map(int, open(0))
n, a, b = map(int, input().split())
# A = list(map(int, input().split()))
# B = list(map(int, input().split()))
# tree = [[] for _ in range(N + 1)]
# B_C = [list(map(int,input().split())) for _ in range(M)]
# S = input()

# B_C = sorted(B_C, reverse=True, key=lambda x:x[1])
# all_cases = list(itertools.permutations(P))
# a = list(itertools.combinations_with_replacement(range(1, M + 1), N))
# itertools.product((0,1), repeat=n)

# A = np.array(A)
# cum_A = np.cumsum(A)
# cum_A = np.insert(cum_A, 0, 0)

# def dfs(tree, s):
#     for l in tree[s]:
#         if depth[l[0]] == -1:
#             depth[l[0]] = depth[s] + l[1]
#             dfs(tree, l[0])
# dfs(tree, 1)

# def factorization(n):
#     arr = []
#     temp = n
#     for i in range(2, int(-(-n**0.5//1))+1):
#         if temp%i==0:
#             cnt=0
#             while temp%i==0:
#                 cnt+=1
#                 temp //= i
#             arr.append([i, cnt])
#     if temp!=1:
#         arr.append([temp, 1])
#     if arr==[]:
#         arr.append([n, 1])
#     return arr

mod = 10 ** 9 + 7

def comb(n, m, mod = 10 ** 9 + 7):
    numerator = 1
    denominator = 1
    for i in range(1, m + 1):
        numerator = numerator * (n - i + 1) % mod
        denominator = denominator * i % mod
    d_inv = pow(denominator, mod - 2, mod)
    return numerator * d_inv % mod

cmb_n_a = comb(n, a)
cmb_n_b = comb(n, b)

print((pow(2, n, mod) - 1 - cmb_n_a - cmb_n_b) % mod)