Compilare: main.cpp: In function 'bool is_prime(long long int)': main.cpp:35:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for( int i = 0; i < prm.size() && prm[i] * prm[i] <= x; ++i ) ~~^~~~~~~~~~~~ main.cpp: In function 'void Do()': main.cpp:45:10: warning: unused variable 'done' [-Wunused-variable] bool done = false; ^~~~