Compilare: main.cpp: In function 'int main()': main.cpp:56:36: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("pinex.in", "r", stdin); ^ main.cpp:57:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("pinex.out", "w", stdout); ^ main.cpp:59:22: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n", &m); ^ main.cpp:64:33: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d\n", &a, &b); ^ main.cpp: In function 'void eratosnenes()': main.cpp:17:19: warning: iteration 500001 invokes undefined behavior [-Waggressive-loop-optimizations] if(!ciur[i]) ~~~~~~^ main.cpp:16:18: note: within this loop for(int i=3;i<=N;i+=2) ^