Compilare: user.cpp: In function ‘void init()’: user.cpp:18:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1 ; i < n.size() ; ++i) ^ user.cpp: In function ‘int main()’: user.cpp:60:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0 ; i < n.size() ; ++i) ^