Compilare: user.cpp:13:6: warning: ISO C++ forbids declaration of ‘main’ with no type [-Wreturn-type] main() ^ user.cpp: In function ‘int main()’: user.cpp:23:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0; i<a.size(); i++) ^ user.cpp:28:40: warning: ‘s’ may be used uninitialized in this function [-Wmaybe-uninitialized] if (s>(n/2)) cout << x << ' ' << s ; else cout << -1; ^