function findMissingNumber(sequence){
  //your code here
  let numbers = sequence.split(' ');

  let seen = new Map();
  for(let num of numbers){
    if(isNaN(num)){
      return 1;
    }
    seen.set(Number(num));
  }

  let it = seen.keys();
  let maybe = [];
  let got = it.next();
  while(!got.done){
    maybe.push(got.value);
    got = it.next();
  }

  maybe = maybe.sort();
  for(let i = 1; i <= maybe[maybe.length-1]; i++){
    console.log(maybe[i]);
    if(maybe[i-1] != i){
      return i
    }
  }
  return 0;
}