Compilare: user.cpp: In function ‘int main()’: user.cpp:25:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("prim.in", "r", stdin); ^ user.cpp:26:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("prim.out", "w", stdout); ^ user.cpp:27:18: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld", &k); ^ user.cpp: In function ‘long long int find(long long int)’: user.cpp:22:1: warning: control reaches end of non-void function [-Wreturn-type] } ^