import std.algorithm;
import std.array;
import std.container;
import std.conv;
import std.math;
import std.numeric;
import std.range;
import std.stdio;
import std.string;
import std.typecons;

void scan(T...)(ref T a) {
    string[] ss = readln.split;
    foreach (i, t; T) a[i] = ss[i].to!t;
}
T read(T)() { return readln.chomp.to!T; }
T[] reads(T)() { return readln.split.to!(T[]); }
alias readint = read!int;
alias readints = reads!int;

const mod = 10^^9 + 7;

long modPow(long x, long k, long m) {
    if (k == 0) return 1;
    if (k % 2 == 0) return modPow(x * x % m, k / 2, m);
    return x * modPow(x, k - 1, m) % m;
}

long nck(long n, long k, long mod) {
    long x = 1;
    for (int i = 0; i < k; i++) {
        x = (x * (n - i)) % mod;
    }
    long kk = iota(1, k+1).reduce!((a, b) => a * b % mod);
    return (x * modPow(kk, mod - 2, mod)) % mod;
}

long calc(long n, long a, long b) {
    long ans = modPow(2, n, mod);
    ans = (ans - nck(n, a, mod) + mod) % mod;
    ans = (ans - nck(n, b, mod) + mod) % mod;
    ans--;
    return ans;
}

void main() {
    int n, a, b; scan(n, a, b);
    writeln(calc(n, a, b));
}
