Compilare: user.cpp: In function ‘void bin(std::string)’: user.cpp:12:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (x.size()==n) ^ user.cpp:14:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<x.size(); i++) ^ user.cpp: At global scope: user.cpp:25:6: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main() ^