text: function range(start, end, step = start < end ? 1 : -1) {
      const result = [];
      if (step >= 0) {
          for (let i = start; i <= end; i += step) {
              result.push(i);
          }
      } else {
          for (let i = start; i >= end; i += step) {
              result.push(i);
          }
      }
      return result;
  }
  
  function sum(arr) {
      let result = 0;
      for (let val of arr) {
          result += val;
      }
      return result;
  }