Compilare: user.cpp: In function ‘long long int sieve(long long int)’: user.cpp:20:13: warning: no return statement in function returning non-void [-Wreturn-type] prim[++u]=i;} ^ user.cpp: In function ‘int main()’: user.cpp:24:17: warning: unused variable ‘j’ [-Wunused-variable] long long a,b,i,j,num,m; ^ user.cpp:22:29: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("nasa.in","r",stdin); ^ user.cpp:23:31: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("nasa.out","w",stdout); ^ user.cpp:25:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld%lld",&a,&b); ^