import java.io.InputStream;
import java.io.IOException;
import java.io.PrintStream;
import java.math.*;
import java.util.*;

public class Main {

  public static void main(String[] args) {
    solve(System.in, System.out);
  }

  private static long MOD = 1000000007;

  static void solve(InputStream is, PrintStream os) {
    Scanner sc = new Scanner(is);

    /* read */
    int n = sc.nextInt();
    int a = sc.nextInt();
    int b = sc.nextInt();

    long ans = 0;

//    ModularNFixedCombination combination = new ModularNFixedCombination(n, 2 * 100000, MOD);
//    Modular modular = new Modular(MOD);
//    ans += modular.pow(2, n);

    ModularNFixedCombination combination = new ModularNFixedCombination(n, 2 * 100000, MOD);
    ans += BigInteger.valueOf(2).modPow(BigInteger.valueOf(n), BigInteger.valueOf(MOD)).longValue();

    long nC0 = 1;
    long nCa = combination.combination(n, a);
    long nCb = combination.combination(n, b);
    ans -= nC0 + nCa + nCb;

    while (ans < 0) {
      ans += MOD;
    }
    os.println(ans);
  }

//  private static class Modular {
//
//    private final long mod;
//
//    private Modular(long mod) {
//      this.mod = mod;
//    }
//
//    private long inverse(long n) {
//      return pow(n, mod - 2) % mod;
//    }
//
//    private long pow(long x, long n) {
//      long ans = 1;
//      while (n > 0) {
//        if ((n & 1) == 1) {
//          ans = ans * x % mod;
//        }
//        x = x * x % mod;
//        n >>= 1;
//      }
//      return ans;
//    }
//  }

  private static class ModularNFixedCombination {

    private final BigInteger[] comb;
    private final long N;

    public ModularNFixedCombination(long N, int size, long mod) {
      this.comb = new BigInteger[size + 1];
      this.N = N;

      comb[0] = BigInteger.ONE;
      BigInteger m = BigInteger.valueOf(mod);

      for (int i = 1; i <= size; i++) {
        comb[i] = comb[i - 1].multiply(BigInteger.valueOf(N - (i - 1))).mod(m)
            .multiply(BigInteger.valueOf(i).modInverse(m)).mod(m);
      }
    }

    long combination(int n, int k) {
      if (n != N) {
        throw new IllegalStateException();
      }
      return comb[k].longValue();
    }
  }

//  private static class ModularNFixedCombination {
//
//    private final Modular modular;
//    private final long[] comb;
//    private final long N;
//
//    public ModularNFixedCombination(long N, int size, long mod) {
//      this.modular = new Modular(mod);
//      this.comb = new long[size + 1];
//      this.N = N;
//
//      comb[0] = 1;
//
//      for (int i = 1; i <= size; i++) {
//        comb[i] = ((comb[i - 1] * (N - (i - 1))) % mod * modular.inverse(i)) % mod;
//      }
//    }
//
//    long combination(int n, int k) {
//      if (n != N) {
//        throw new IllegalStateException();
//      }
//      return comb[k];
//    }
//  }

//  private static class ModularCombination {
//
//    private final long fact[];
//    private final long mod;
//    private final Modular modular;
//
//    public ModularCombination(int size, long mod) {
//      this.fact = new long[size + 1];
//      this.mod = mod;
//      this.modular = new Modular(mod);
//
//      this.fact[0] = 1;
//      for (int i = 1; i <= size; i++) {
//        fact[i] = (fact[i - 1] * i) % mod;
//      }
//    }
//
//    private long factorial(int n) {
//      return fact[n];
//    }
//
//    long combination(int n, int k) {
//      return
//          (
//              (
//                  (
//                      factorial(n) * modular.inverse(factorial(n - k))
//                  ) % mod
//              ) * modular.inverse(factorial(k))
//          ) % mod;
//    }
//  }

  private static class Scanner {

    private final InputStream is;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int buflen = 0;

    Scanner(InputStream is) {
      this.is = is;
    }

    private boolean hasNextByte() {
      if (ptr < buflen) {
        return true;
      } else {
        ptr = 0;
        try {
          buflen = is.read(buffer);
        } catch (IOException e) {
          e.printStackTrace();
        }
        if (buflen <= 0) {
          return false;
        }
      }
      return true;
    }

    private int readByte() {
      if (hasNextByte()) {
        return buffer[ptr++];
      } else {
        return -1;
      }
    }

    private static boolean isPrintableChar(int c) {
      return 33 <= c && c <= 126;
    }

    public boolean hasNext() {
      while (hasNextByte() && !isPrintableChar(buffer[ptr])) {
        ptr++;
      }
      return hasNextByte();
    }

    public String next() {
      if (!hasNext()) {
        throw new NoSuchElementException();
      }
      StringBuilder sb = new StringBuilder();
      int b = readByte();
      while (isPrintableChar(b)) {
        sb.appendCodePoint(b);
        b = readByte();
      }
      return sb.toString();
    }

    public long nextLong() {
      if (!hasNext()) {
        throw new NoSuchElementException();
      }
      long n = 0;
      boolean minus = false;
      int b = readByte();
      if (b == '-') {
        minus = true;
        b = readByte();
      }
      if (b < '0' || '9' < b) {
        throw new NumberFormatException();
      }
      while (true) {
        if ('0' <= b && b <= '9') {
          n *= 10;
          n += b - '0';
        } else if (b == -1 || !isPrintableChar(b)) {
          return minus ? -n : n;
        } else {
          throw new NumberFormatException();
        }
        b = readByte();
      }
    }

    public int nextInt() {
      long nl = nextLong();
      if (nl < Integer.MIN_VALUE || nl > Integer.MAX_VALUE) {
        throw new NumberFormatException();
      }
      return (int) nl;
    }

    public double nextDouble() {
      return Double.parseDouble(next());
    }
  }
}


Measured memory_bytes: 113804