Compilare: user.cpp: In function ‘int main()’: user.cpp:44:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<expresie.size()){ ^ user.cpp:50:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i<expresie.size() && expresie[i]>='0' && expresie[i]<='9') ^