#include <bits/stdc++.h>
using namespace std;

const long long MOD = 1000000007;



struct GCDResult{long long x; long long y; long long res;};
GCDResult gcd(long long a, long long b){
    if(a < 0){
        auto sub = gcd(-a, b);
        return GCDResult{-sub.x, sub.y, sub.res};
    }
    if(b < 0){
        auto sub = gcd(a, -b);
        return GCDResult{sub.x, -sub.y, sub.res};
    }
    if(a < b){
        auto sub = gcd(b, a);
        return GCDResult{sub.y, sub.x, sub.res};
    }
    // a >= b AND a >= 0 AND b >= 0
    if(b == 0){
        return GCDResult{1LL, 0LL, a};
    }
    // a >= b AND a > 0 AND b > 0
    auto sub = gcd(b, a % b);
    return GCDResult{sub.y, sub.x - sub.y*(a/b), sub.res};
}

template <long long p>
class Zp{
    long long content;
    public:
    Zp(long long content_){
        if(content_ >= 0){
            content = content_ % p;
        }else{
            long long temp = p;
            while(temp < -content_){
                temp *= p;
            }
            content = (temp + content_) % p;
        }
    }

    bool operator==(const Zp<p>& rhs) const{
        return this->content == rhs.content;
    }

    bool operator!=(const Zp<p>& rhs) const{
        return !(*this == rhs);
    }

    Zp<p> operator+(const Zp<p>& rhs) const{
        return Zp<p>(this->content + rhs.content);
    }

    Zp<p> operator-() const{
        return Zp<p>(p - this->content);
    }

    Zp<p> operator-(const Zp<p>& rhs) const{
        return Zp<p>(this->content - rhs.content + p);
    }

    Zp<p> operator*(const Zp<p>& rhs) const{
        return Zp<p>(this->content * rhs.content);
    }

    Zp<p> inv() const{
        if(this->content == 0){
            assert(false);
        }

        auto res = gcd(this->content, p);
        return Zp<p>(res.x);
    }

    Zp<p> operator/(const Zp<p>& rhs) const{
        if(rhs.content == 0){
            assert(false);
        }
        
        return (*this)*rhs.inv();
    }

    Zp<p> pow(int n){
        auto res = Zp<p>(1);
        Zp<p> mult = (*this);
        while(n > 0){
            if(n & 1 == 1){
                res = res*mult;
            }
            n >>= 1;
            mult = mult*mult;
        }
        return res;
    }

    long long raw(){
        return this->content;
    }

};

Zp<MOD> twopow(long long n){
    auto res = Zp<MOD>(1);
    auto powed = Zp<MOD>(2);
    while(n != 0){
        if(n&1 != 0){
            res = res * powed;
            
        }
        powed = powed*powed;
        n >>= 1;
    }
    return res;
}

Zp<MOD> hoge(long long n, long long k){
    Zp<MOD> res = Zp<MOD>(1);
    for(int i=1; i <= k; i++){
        res = res*Zp<MOD>(n + 1 - i)/Zp<MOD>(i);
    }
    return res;
}


void solve(long long n, long long a, long long b){
    auto res = twopow(n) - Zp<MOD>(1) - hoge(n, a) - hoge(n, b);    
    cout << res.raw() << endl;

}

// Generated by 1.1.6 https://github.com/kyuridenamida/atcoder-tools  (tips: You use the default template now. You can remove this line by using your custom template)
int main(){
    // COMinit();
    // cout << twopow(4).raw() << endl;

    long long n;
    scanf("%lld",&n);
    long long a;
    scanf("%lld",&a);
    long long b;
    scanf("%lld",&b);
    solve(n, a, b);
    return 0;
}


Measured memory_bytes: 384