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;

// dfmt off
T lread(T = long)(){return readln.chomp.to!T();}
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);
    writeln((MOD * 2 + powmod(2, N) - 1 - c(N, A) - c(N, B)) % MOD);
}

long c(long n, long k)
{
    long a = 1, b = 1;
    foreach (i; 0 .. k)
    {
        a = a * (n - i) % MOD;
        b = b * (i + 1) % MOD;
    }
    return a * powmod(b, MOD - 2) % MOD;
}

/// x^^n % m
T powmod(T = long)(T x, T n, T m = 10 ^^ 9 + 7)
{
    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;
}
