foo.cc: In function ‘int main()’:
foo.cc:41:23: warning: ‘d’ may be used uninitialized [-Wmaybe-uninitialized]
   41 |         cout<<c<<" "<<d<<endl;
      |                       ^
foo.cc:17:19: note: ‘d’ was declared here
   17 |         int a,b,c,d,flag;
      |                   ^