Compilare: user.cpp: In function ‘int main()’: user.cpp:11:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] { freopen("light2.in","r",stdin); freopen("light2.out","w",stdout); ^ user.cpp:11:69: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] { freopen("light2.in","r",stdin); freopen("light2.out","w",stdout); ^ user.cpp:12:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%lld%d", &n,&k); ^ user.cpp:13:40: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] for(i=1;i<=k;++i) scanf("%d",&a[i]); ^