Compilare: main.cpp: In function 'int main()': main.cpp:11:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=1,j=0; i<b.size(); ++i) { ~^~~~~~~~~ main.cpp:21:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i=0, j=0; i<a.size(); ++i) { ~^~~~~~~~~