Compilare: user.cpp: In function ‘void read()’: user.cpp:17:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<a.size(); i++) ^ user.cpp:20:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j=0; j<a[i].size(); j++) ^ user.cpp: In function ‘void vu(std::vector<std::vector<int> >)’: user.cpp:46:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (s.size()!=q) ^ user.cpp:48:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<a[0].size(); i++) ^ user.cpp:51:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (q<=s.size()) break; ^ user.cpp:52:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<a.size(); i++) ^ user.cpp:57:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (q<=s.size()) break; ^ user.cpp:61:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (q<=s.size()) break; ^ user.cpp: In function ‘void solve()’: user.cpp:73:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=1; i<s.size(); i++) ^ user.cpp: At global scope: user.cpp:78:6: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main() ^