text: function findNonRepetativeNumber(arr){
      let res;
      for(let i=0; i<arr.length; i+=1) {
        res = arr[i] ^ arr[i+1];
      }
      return res;
     };
  
  let arr = [-1, 2, 5, 6, 2, 9, -1, 6, 5, -1, 3];
  
  console.log(findNonRepetativeNumber(arr));
  