Compilare: main.cpp: In function 'int main()': main.cpp:64:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (pa != a.size() && pb != b.size()) { ~~~^~~~~~~~~~~ main.cpp:64:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (pa != a.size() && pb != b.size()) { ~~~^~~~~~~~~~~