pipe.cpp: In function 'int main()': pipe.cpp:56: error: call of overloaded 'abs(int)' is ambiguous /usr/include/c++/4.4/cmath:94: note: candidates are: double std::abs(double) /usr/include/c++/4.4/cmath:98: note: float std::abs(float) /usr/include/c++/4.4/cmath:102: note: long double std::abs(long double) pipe.cpp:57: error: call of overloaded 'abs(int)' is ambiguous /usr/include/c++/4.4/cmath:94: note: candidates are: double std::abs(double) /usr/include/c++/4.4/cmath:98: note: float std::abs(float) /usr/include/c++/4.4/cmath:102: note: long double std::abs(long double) pipe.cpp:58: warning: unused variable 'k'