var twoSum = function(nums, target) {
  var i = 0;
  var j = 0;
  for (i = nums.length-1; i >= 0; i--){
    for (j = i-1; j >= 0; j--){
      if (nums[i] + nums[j] === target){
        return [j, i];
      }
    }
  }
    
  return null;
};