Write It in Binary

Write to_binary(n) that returns the binary representation of the non-negative integer n as a string, without using bin() or format().

Examples

Input:  n = 5
Output: "101"

Input:  n = 0
Output: "0"

Input:  n = 255
Output: "11111111"

Constraints

• 0 <= n <= 2**60
• No leading zeros (except for the single "0").

Goals

• Convert with repeated division by 2
• Build a string in the right order
• Special-case zero