Compilare: main.cpp: In function 'int main()': main.cpp:21:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i = 0; n > 1 and i < pr.size() and pr[i] * pr[i] <= n; i++) ~~^~~~~~~~~~~ main.cpp:11:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("perechi.in", "r", stdin); ^ main.cpp:12:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("perechi.out", "w", stdout); ^ main.cpp:20:20: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &n); ^ main.cpp:14:16: warning: iteration 23171 invokes undefined behavior [-Waggressive-loop-optimizations] if(!c[i]) for(int k = i * i; k <= 46345; k += i) ~~~^ main.cpp:13:22: note: within this loop for(int i = 3; i <= 46345; i += 2) ~~^~~~~~~~