Compilare: user.cpp: In function ‘void make_prefix()’: user.cpp:14:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 2; i < A.size(); ++i) { ^ user.cpp: In function ‘int main()’: user.cpp:34:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i < B.size(); ++i) { ^ user.cpp:39:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (q == A.size() - 1) { ^