Compilare: main.cpp: In function 'int main()': main.cpp:83:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a.size();i++) ~^~~~~~~~~ main.cpp:86:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<b.size();i++) ~^~~~~~~~~ main.cpp:89:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<c.size();i++) ~^~~~~~~~~