def main():

    #input data

    import sys

    input = lambda:sys.stdin.readline().strip()

    

    N,A,B = list(map(int,input().split()))

    mod=10**9+7

    #solve

    #二項係数の和=2**n

    #2**n-1-nCa-nCb

    def cmb(n, r, mod=10**9+7):

        r = min(r, n-r)

        res = 1

        for i in range(r):

            res = res * (n - i) * pow(i+1, mod-2, mod) % mod

        return res

                

    ans = pow(2,N,mod)-1-cmb(N,A,mod)-cmb(N,B,mod)

    print((ans%mod))



if __name__=='__main__':

    main()
def main():

    #input data

    import sys

    input = lambda:sys.stdin.readline().strip()

    

    N,A,B = list(map(int,input().split()))

    mod=10**9+7

    #solve

    #二項係数の和=2**n

    #2**n-1-nCa-nCb

    

    def cmb(n, r, mod=10**9+7):

        c = 1

        m = 1

        r = min(n - r, r)

        for i in range(r):

            c = c * (n - i) % mod

            m = m * (i + 1) % mod

        return c * pow(m, mod - 2, mod) % mod

                

    ans = pow(2,N,mod)-1-cmb(N,A,mod)-cmb(N,B,mod)

    print((ans%mod))



if __name__=='__main__':

    main()
def main():
    # input data
    import sys

    input = lambda: sys.stdin.readline().strip()
    N, A, B = list(map(int, input().split()))
    mod = 10**9 + 7
    # solve
    # 二項係数の和=2**n
    # 2**n-1-nCa-nCb
    def cmb(n, r, mod=10**9 + 7):
        r = min(r, n - r)
        res = 1
        for i in range(r):
            res = res * (n - i) * pow(i + 1, mod - 2, mod) % mod
        return res

    ans = pow(2, N, mod) - 1 - cmb(N, A, mod) - cmb(N, B, mod)
    print((ans % mod))


if __name__ == "__main__":
    main()

def main():
    # input data
    import sys

    input = lambda: sys.stdin.readline().strip()
    N, A, B = list(map(int, input().split()))
    mod = 10**9 + 7
    # solve
    # 二項係数の和=2**n
    # 2**n-1-nCa-nCb
    def cmb(n, r, mod=10**9 + 7):
        c = 1
        m = 1
        r = min(n - r, r)
        for i in range(r):
            c = c * (n - i) % mod
            m = m * (i + 1) % mod
        return c * pow(m, mod - 2, mod) % mod

    ans = pow(2, N, mod) - 1 - cmb(N, A, mod) - cmb(N, B, mod)
    print((ans % mod))


if __name__ == "__main__":
    main()

-        r = min(r, n - r) -        res = 1 +        c = 1 +        m = 1 +        r = min(n - r, r) -            res = res * (n - i) * pow(i + 1, mod - 2, mod) % mod -        return res +            c = c * (n - i) % mod +            m = m * (i + 1) % mod +        return c * pow(m, mod - 2, mod) % mod