foo.cpp: In function 'int main()':
foo.cpp:145:16: error: 'abs' was not declared in this scope
   if (abs(b - a) == numOfVec / 2) {
                ^
foo.cpp:145:16: note: suggested alternative:
In file included from foo.cpp:12:0:
c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\cmath:99:5: note:   'std::abs'
     abs(_Tp __x)
     ^
foo.cpp:171:16: error: 'abs' was not declared in this scope
   if (abs(b - a) < numOfVec / 2) {
                ^
foo.cpp:171:16: note: suggested alternative:
In file included from foo.cpp:12:0:
c:\mingw\lib\gcc\mingw32\4.8.1\include\c++\cmath:99:5: note:   'std::abs'
     abs(_Tp __x)
     ^