Compilare: user.cpp: In function ‘void extract(int, int)’: user.cpp:16:9: warning: unused variable ‘x’ [-Wunused-variable] int x, y; ^ user.cpp:16:12: warning: unused variable ‘y’ [-Wunused-variable] int x, y; ^ user.cpp: In function ‘int main()’: user.cpp:68:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0 ; i < comp.size() ; i++) ^