Format any integer provided into a string with "," (commas) in the correct places.
**Example:**
``` csharp
Kata.NumberFormat(100000); // return "100,000"
Kata.NumberFormat(5678545); // return "5,678,545"
Kata.NumberFormat(-420902); // return "-420,902"
```
``` javascript
numberFormat(100000); // return '100,000'
numberFormat(5678545); // return '5,678,545'
numberFormat(-420902); // return '-420,902'
```
``` cpp
numberFormat(100000); // return '100,000'
numberFormat(5678545); // return '5,678,545'
numberFormat(-420902); // return '-420,902'
```
``` python
number_format(100000); # return '100,000'
number_format(5678545); # return '5,678,545'
number_format(-420902); # return '-420,902'
```
``` ruby
number_format(100000); # return '100,000'
number_format(5678545); # return '5,678,545'
number_format(-420902); # return '-420,902'
```
``` crystal
number_format(100000); # return '100,000'
number_format(5678545); # return '5,678,545'
number_format(-420902); # return '-420,902'
```
def number_format(n):
  n = [x for x in str(n)]
  if n[0] == "-":
    n = n[1:]
    result = "-"
  else:
    result = ""
  end = []
  while len(n) > 3:
    end.append("".join([","]+n[-3:]))
    n = n[:-3]
  end.append("".join(n))
  for x in end:
    result += end[-1]
    end = end[:-1]
  return result
def number_format(n):
  n = [x for x in str(n)]
  if n[0] == "-":
    n = n[1:]
    result = "-"
  else:
    result = ""
  end = []
  while len(n) > 3:
    end.append("".join([","]+n[-3:]))
    n = n[:-3]
  end.append("".join(n))
  for x in end:
    result += end[-1]
    end = end[:-1]
  return result