Add Thousand Separators to a Number String

Easy ⏱ 8 min 75% acceptance ★★★★☆ 4.3

Write add_thousand_separators(n) that converts an integer n into a string with commas every three digits from the right (e.g. 1234567 becomes "1,234,567"), preserving a leading minus sign for negative numbers.

Examples

Example 1

Input

n = 1234567

Output

'1,234,567'

Explanation

Digits are grouped into threes from the right.

Example 2

Input

n = -4200

Output

'-4,200'

Explanation

The minus sign is kept in front, outside the grouping logic.

Example 3

Input

n = 42

Output

'42'

Explanation

Numbers under 1000 need no comma.

Constraints

n is an integer (can be negative or zero).

Topics

StringsString Building

Companies

WalmartFlipkart

Hints

Hint 1

Work with `str(abs(n))` and peel off the last 3 characters repeatedly.

Hint 2

Re-attach the minus sign at the end if n was negative.

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