Compilare: user.cpp: In function ‘void read()’: user.cpp:25:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<a.size(); i++) ^ user.cpp: In function ‘void solve()’: user.cpp:44:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<a.size(); i++) ^ user.cpp:46:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=i+1; j<a.size(); j++) ^ user.cpp: At global scope: user.cpp:55:6: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main() ^