Compilare: user.cpp: In function ‘bool bf(int)’: user.cpp:29:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0; i<v[start].size(); i++) ~^~~~~~~~~~~~~~~~ user.cpp:43:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(j=0; j<v[i].size(); j++) ~^~~~~~~~~~~~ user.cpp: In function ‘int main()’: user.cpp:68:10: warning: unused variable ‘ok’ [-Wunused-variable] bool ok=bf(ans); ^~