Main.cc: In function ‘int main()’: Main.cc:10:29: error: ‘__popcntd’ was not declared in this scope cin>>n,r=len=__lg(n)+!!(__popcntd(n)-1),t=len+1; ^~~~~~~~~ Main.cc:10:29: note: suggested alternative: ‘__round’ cin>>n,r=len=__lg(n)+!!(__popcntd(n)-1),t=len+1; ^~~~~~~~~ __round Main.cc:9:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("telegram.in","r",stdin),freopen("telegram.out","w",stdout); ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Main.cc:9:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result]