Compilare: main.cpp: In function 'int main()': main.cpp:18:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i<a.size(); i++) ~^~~~~~~~~ main.cpp:20:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j<b.size(); j++) ~^~~~~~~~~ main.cpp:31:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i =0; i<a.size(); i++) ~^~~~~~~~~ main.cpp:33:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j<b.size(); j++) ~^~~~~~~~~