Compilare: user.cpp: In function ‘void prime()’: user.cpp:13:39: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int p, x = 1; x * x < a.size(); x++) ^ user.cpp:14:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int y = 1; y * y < a.size(); y++) ^ user.cpp:17:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (p < a.size() && (p % 12 == 1 || p % 12 == 5)) ^ user.cpp:20:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (p < a.size() && p % 12 == 7) ^ user.cpp:23:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (x > y && p < a.size() && p % 12 == 11) ^ user.cpp:27:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 5; i * i< a.size(); i++) ^ user.cpp:29:50: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int k = i * i, q = k; k< a.size(); k += q) a[k] = false; ^