import core.bitop, std.algorithm, std.ascii, std.bigint, std.conv, std.math,
    std.functional, std.numeric, std.range, std.stdio, std.string, std.random,
    std.typecons, std.container, std.format;
static import std.ascii;

// dfmt off
T lread(T = long)(){return readln.chomp.to!T();}
T[] lreads(T = long)(long n){return generate(()=>readln.chomp.to!T()).take(n).array();}
T[] aryread(T = long)(){return readln.split.to!(T[])();}
void scan(TList...)(ref TList Args){auto line = readln.split();
foreach (i, T; TList){T val = line[i].to!(T);Args[i] = val;}}
alias sread = () => readln.chomp();enum MOD = 10 ^^ 9 + 7;
alias PQueue(T, alias less = "a<b") = BinaryHeap!(Array!T, less);
// dfmt on

void main()
{
    long N, A, B;
    scan(N, A, B);
    long ans = MOD + powmod(2, N, MOD) - 1;
    ans %= MOD;
    auto f = new long[](B + 1);
    f[0] = 1;
    foreach (i; 1 .. B + 1)
        f[i] = (f[i - 1] * i) % MOD;

    long xa = 1;
    foreach (i; (N - A + 1) .. N + 1)
        xa *= i, xa %= MOD;

    long xb = 1;
    foreach (i; (N - B + 1) .. N + 1)
        xb *= i, xb %= MOD;

    auto ca = xa * invmod(f[A]) % MOD;
    auto cb = xb * invmod(f[B]) % MOD;
    writeln((ans + 2 * MOD - ca - cb) % MOD);

}

T powmod(T = long)(T x, T n, T m)
{
    if (n < 1)
        return 1;
    if (n & 1)
    {
        return x * powmod(x, n - 1, m) % m;
    }
    T tmp = powmod(x, n / 2, m);
    return tmp * tmp % m;
}

T invmod(T = long)(T x, T m = 10 ^^ 9 + 7)
{

    return powmod(x, m - 2, m);
}
