Compilare: main.cpp: In function 'int main()': main.cpp:38:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<a.size(); i++) ~^~~~~~~~~ main.cpp:66:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<a.size(); i++) ~^~~~~~~~~ main.cpp:55:21: warning: variable 'ok' set but not used [-Wunused-but-set-variable] int ok=1; ^~