import math
from functools import reduce
from collections import deque
import sys
sys.setrecursionlimit(10**7)

# スペース区切りの入力を読み込んで数値リストにして返します。
def get_nums_l():
    return [ int(s) for s in input().split(" ")]

# 改行区切りの入力をn行読み込んで数値リストにして返します。
def get_nums_n(n):
    return [ int(input()) for _ in range(n)]

# 改行またはスペース区切りの入力をすべて読み込んでイテレータを返します。
def get_all_int():
    return map(int, open(0).read().split())

def log(*args):
    print("DEBUG:", *args, file=sys.stderr)

def inv(x):
    return pow(x, MOD-2, MOD)

def nPk(n,k):
    x = 1
    for a in range(n-k+1, n+1):
        x = x * a % MOD
    return x

def nCk(n,k):
    return nPk(n,k) * inv(kaijo[k])

MOD = 10**9+7

kaijo = [0] * 400020
kaijo[0] = 1
for i in range(1, len(kaijo)):
    kaijo[i] = kaijo[i-1] * i % MOD

# def fac(N):
#     known = { 0: 1, 1000000000: 698611116, 320000000: 30977140, 820000000: 629786193, 740000000: 375297772, 470000000: 909210595, 200000000: 933245637, 940000000: 83868974, 400000000: 429277690, 130000000: 623534362, 870000000: 256473217, 600000000: 724464507, 330000000: 522049725, 60000000: 27368307, 800000000: 203191898, 530000000: 256141983, 260000000: 135498044, 730000000: 663307737, 460000000: 275105629, 190000000: 109838563, 930000000: 778983779, 660000000: 769795511, 390000000: 917084264, 120000000: 661224977, 860000000: 116667533, 10000000: 682498929, 590000000: 131772368, 50000000: 67347853, 790000000: 748510389, 520000000: 608823837, 250000000: 112390913, 990000000: 847549272, 720000000: 852304035, 450000000: 462639908, 180000000: 547665832, 920000000: 193781724, 650000000: 92255682, 380000000: 940567523, 110000000: 281863274, 850000000: 823845496, 580000000: 848924691, 310000000: 128487469, 40000000: 723816384, 780000000: 624500515, 510000000: 97830135, 240000000: 136026497, 980000000: 377329025, 710000000: 435887178, 440000000: 780072518, 170000000: 66404266, 20000000: 491101308, 670000000: 373745190, 910000000: 172114298, 640000000: 903466878, 370000000: 148528617, 100000000: 927880474, 840000000: 814362881, 570000000: 811575797, 300000000: 668123525, 30000000: 76479948, 770000000: 671734977, 500000000: 733333339, 230000000: 268838846, 970000000: 492741665, 700000000: 957939114, 430000000: 568392357, 160000000: 195888993, 900000000: 586445753, 630000000: 456152084, 360000000: 189239124, 90000000: 888050723, 830000000: 672850561, 560000000: 637939935, 290000000: 500780548, 760000000: 624148346, 490000000: 703397904, 220000000: 368925948, 270000000: 217544623, 960000000: 965785236, 690000000: 825871994, 420000000: 358655417, 150000000: 261384175, 890000000: 245795606, 620000000: 326159309, 350000000: 386027524, 80000000: 199888908, 550000000: 696628828, 280000000: 419363534, 750000000: 217598709, 480000000: 99199382, 210000000: 724691727, 950000000: 315103615, 680000000: 606241871, 410000000: 996164327, 140000000: 970055531, 880000000: 627655552, 610000000: 272814771, 340000000: 309058615, 70000000: 625544428, 810000000: 423951674, 540000000: 141827977}

#     ans = known[ N - N % int( 1e7 ) ]
#     for i in range( N - N % int( 1e7 ) + 1, N + 1, 1 ):
#         ans = ans * i % MOD
#     return ans

n,a,b = get_nums_l()

nCa = nCk(n,a)
nCb = nCk(n,b)
ans = pow(2, n, MOD) - 1 - nCa - nCb
print(ans % (10**9 + 7))

Measured memory_bytes: 41968