Converting a sequence of digits into Russian letters

Create a function that takes a string in which numbers from 1 to 33 are separated by spaces. Each number corresponds to a letter of the Russian alphabet according to the reference {а: 1, б: 2, в: 3, ..., я: 33}. The function should return a string composed of the letters corresponding to the given numbers.

Example 1: Input: "1 2 3" Output: "абв"

Example 2: Input: "33 2 13 16 12 16" Output: "яблоко"