text: 'use strict';
  
  let arr = [];
  
  function fibonacci(num) {
    arr.push(num);
    if (num <= 1) {
      arr.push(1);
      return 1;
    }
    let number = fibonacci(num - 1) + fibonacci(num - 2);
    return number;   
  }
  
  fibonacci(6);
  
  
  function printAll(arr, k){
    let n = arr.length;
    stringCombos(arr, '', n, k);
  }
  
  function stringCombos(arr, str, n, k){
    if(k === 0){
      return;
    }
    for( let i = 0; i < n; ++i){
      let newStr;
      if(str.split('').includes(arr[i])){
        newStr = '';
      }
      else{
        newStr = str + arr[i];
        stringCombos(arr, newStr, n, k-1);
      }
    }
  }
  
  
  printAll(['1', '2', '3'], 3);