Implement a function string convertToNS(int num, int base) that uses a stack to convert a number from decimal notation to a number expressed in a number system whose base (or radix) is a number between 2 and 20. The conversion is performed by repetitious division by the base to which a number is being converted and then taking the remainders of division in the reverse order. Note that numbering systems >=11 will require more symbols to represent their digits. Use capital letters, starting with A, B, C, ..., etc. Example input: number:61 , base: 3. Output: 2021. Example input: number:125 , base: 18. Output: 6H.