text: function solution() {
      let string = '';
      return {
          append: (str) => string += str,
          removeStart: (n) => string = string.substring(n),
          removeEnd: (n) => string = string.substring(0, string.length - n),
          print: () => console.log(string)
      }
  }
  
  let firstZeroTest = solution();
  
  firstZeroTest.append('hello');
  firstZeroTest.append('again');
  firstZeroTest.removeStart(3);
  firstZeroTest.removeEnd(4);
  firstZeroTest.print();
  
  let secondZeroTest = solution();
  
  secondZeroTest.append('123');
  secondZeroTest.append('45');
  secondZeroTest.removeStart(2);
  secondZeroTest.removeEnd(1);
  secondZeroTest.print();
  