text: 'use strict';
  
  function sumZero(arr){
    if(arr.length < 1 || typeof arr !== 'object') {
      return 'Error occurred. Please enter a valid array.';
    }
  
    let left = 0;
    let right = arr.length - 1;
  
    while (left < right) {
      let sum = arr[left] + arr[right];
      if (sum === 0) {
        return [arr[left], arr[right]];
      } else if ( sum > 0) {
        right--;
      } else {
        left++;
      }
    }
    return null;
  }
  
  module.exports = sumZero;
  