Compilare: main.cpp: In function 'int main()': main.cpp:20:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=1; i<=b.size(); ++i) ~^~~~~~~~~~ main.cpp:22:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=a.size()-1; i<b.size(); ++i) ~^~~~~~~~~