Compilare: main.cpp: In function 'int main(int, const char**)': main.cpp:19:35: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("ciur.in", "r", stdin); ^ main.cpp:20:37: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("ciur.out", "w", stdout); ^ main.cpp:23:20: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ main.cpp:26:14: warning: iteration 2000001 invokes undefined behavior [-Waggressive-loop-optimizations] v[i] = true; ~~~~~^~~~~~ main.cpp:25:20: note: within this loop for (int i=0; i<=IMAX; i++) ~^~~~~~