Compilare: user.cpp: In function ‘void solve()’: user.cpp:38:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=1; i<a.size(); i++) ^ user.cpp:40:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=1; i<b.size(); i++) ^ user.cpp:42:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=1; i<a.size(); i++) ^ user.cpp:43:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=1; j<b.size(); j++) ^ user.cpp: At global scope: user.cpp:55:6: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main() ^