abs, labs, llabs, imaxabs - compute the absolute value of an integer
Returns the absolute value of the integer argument, of the appropriate integer type for the function.
Trying to take the absolute value of the most negative integer is not defined.
For llabs() to be declared, it may be necessary to define _ISOC99_SOURCE or _ISOC9X_SOURCE (depending on the version of glibc) before including any standard headers.
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