Error(s):

source_file.cpp: In function ‘int main()’:
source_file.cpp:6:5: error: ‘sample::~sample()’ is private
     ~sample(){
     ^
source_file.cpp:14:12: error: within this context
     delete a1;
            ^
source_file.cpp:13:10: warning: unused variable ‘a2’ [-Wunused-variable]
  sample *a2=new sample();
          ^