abs, labs, llabs, imaxabs
From cppreference.com
                    
                                        
                    
                    
                                                            
                    |   Defined in header <stdlib.h>
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|   int        abs( int n );  | 
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|   long       labs( long n );  | 
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|   long long llabs( long long n );  | 
(since C99) | |
|   Defined in header <inttypes.h>
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|   intmax_t imaxabs( intmax_t n );  | 
(since C99) | |
Computes the absolute value of an integer number.
[edit] Parameters
| n | - | integer value | 
[edit] Return value
The absolute value of n (i.e. |n|)
[edit] See also
|    absolute value of a floating point value (|x|)   (function)  | |
|   C++ documentation for abs 
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