Compilare: main.cpp: In function 'int main()': main.cpp:96:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("intrus.in", "r", stdin); ^ main.cpp:97:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen ("intrus.out", "w", stdout); ^ main.cpp: In function 'void sieve()': main.cpp:38:19: warning: iteration 500001 invokes undefined behavior [-Waggressive-loop-optimizations] if (comp[i]) continue; ~~~~~~^ main.cpp:37:23: note: within this loop for (int i = 3; i <= VMAX; i += 2) { ~~^~~~~~~