#include <bits/stdc++.h>
#include <time.h>
#include <stdlib.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define pb push_back
#define IOS ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define ll long long
#define ull unsigned long long
#define gcd(a,b) __gcd((a),(b))
#define lcm(a,b) ((a)*(b))/__gcd((a),(b))
#define clr(x) x.clear()
#define vi vector<int>
#define vll vector<long long>
#define vvi vector<vi>
#define mp make_pair
#define hell 1000000007
#define pii pair<int,int>
#define pll pair<ll,ll>
#define vpii vector<pii>
#define vpll vector<pll>
#define all(a) a.begin(),a.end()
#define ign cin.ignore();

#define o_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update>
#define o_setll tree<ll, null_type,less<ll>, rb_tree_tag,tree_order_statistics_node_update>
//member functions :
//1. order_of_key(k) : number of elements strictly lesser than k
//2. find_by_order(k) : k-th element in the set

using namespace std;
using namespace __gnu_pbds;

void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}

template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif

// ---------- mulmod and powmod from my toolbox ----------

// return (a*b) % modulo
unsigned long long mulmod(unsigned long long a, unsigned long long b, unsigned long long modulo)
{
  // (a * b) % modulo = (a % modulo) * (b % modulo) % modulo
  a %= modulo;
  b %= modulo;

  // fast path
  if (a <= 0xFFFFFFF && b <= 0xFFFFFFF)
    return (a * b) % modulo;

  // we might encounter overflows (slow path)
  // the number of loops depends on b, therefore try to minimize b
  if (b > a)
    std::swap(a, b);

  // bitwise multiplication
  unsigned long long result = 0;
  while (a > 0 && b > 0)
  {
    // b is odd ? a*b = a + a*(b-1)
    if (b & 1)
    {
      result += a;
      if (result >= modulo)
        result -= modulo;
      // skip b-- because the bit-shift at the end will remove the lowest bit anyway
    }

    // b is even ? a*b = (2*a)*(b/2)
    a <<= 1;
    if (a >= modulo)
      a -= modulo;

    // next bit
    b >>= 1;
  }

  return result;
}

// return (base^exponent) % modulo => simple implementation
unsigned long long powmod(unsigned long long base, unsigned long long exponent, unsigned long long modulo)
{
  unsigned long long result = 1;
  while (exponent > 0)
  {
    // fast exponentation:
    // odd exponent ? a^b = a*a^(b-1)
    if (exponent & 1)
      result = mulmod(result, base, modulo);

    // even exponent ? a^b = (a*a)^(b/2)
    base = mulmod(base, base, modulo);
    exponent >>= 1;
  }
  return result;
}

ll mul_inv(ll a, ll b)
{
    ll b0 = b, t, q;
    ll x0 = 0, x1 = 1;
    if (b == 1) return 1;
    while (a > 1) {
        q = a / b;
        t = b, b = a % b, a = t;
        t = x0, x0 = x1 - q * x0, x1 = t;
    }
    if (x1 < 0) x1 += b0;
    return x1;
}

int main()
{
    IOS
    ll n,a,b;
    cin>>n>>a>>b;
    ll base=powmod(2,n,hell);
    base-=1;
    ll mult1=1,mult2=1;
    for(ll i=n;i>n-a;i--)
    {
        mult1=(mult1*i)%hell;
    }
    for(ll i=n;i>n-b;i--)
    {
        mult2=(mult2*i)%hell;
    }
    ll a_fac=1,b_fac=1;
    for(ll i=2;i<=a;i++)
    {
        a_fac=(a_fac*i)%hell;
    }
    for(ll i=2;i<=b;i++)
    {
        b_fac=(b_fac*i)%hell;
    }

    ll mul1=mul_inv(a_fac,hell);
    ll mul2=mul_inv(b_fac,hell);

    ll ret1=mulmod(mul1,mult1,hell);
    ll ret2=mulmod(mul2,mult2,hell);

    ll res=(base+hell-ret1)%hell;
    res=(res+hell-ret2)%hell;

    cout<<res;

    return 0;
}


Measured memory_bytes: 256