Compilare: user.cpp: In function ‘int mod()’: user.cpp:14:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) ^ user.cpp: In function ‘void aduna(int)’: user.cpp:33:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < s.size(); i++) { ^