Compilare: main.cpp: In function 'int main()': main.cpp:62:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1; i<a1.size(); i++) ~^~~~~~~~~~ main.cpp:66:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1; i<a2.size(); i++) ~^~~~~~~~~~