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:37:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i < B.size(); i++){ ^