"use strict";
function main(input) {
  let kari = input[0].trim().split(" ");
  let n = parseInt(kari[0]);
  let a = parseInt(kari[1]);
  let b = parseInt(kari[2]);

  let bunbo = 1;
  let bunshi = 1;

  let sum = 0;
  for(let i=1;i<n+1;i++){
    bunshi *= (n+1-i);
    bunbo *= i;
    if(i!==a && i!==b){
      sum += (bunshi/bunbo);
    }
  }
  console.log(sum%(Math.pow(10,9)+7));
}
main(require('fs').readFileSync('/dev/stdin', 'utf8').trim().split("\n"));