foo.cc: In function ‘int main()’:
foo.cc:21:15: warning: ‘b’ may be used uninitialized [-Wmaybe-uninitialized]
   21 |         cout<<b;
      |               ^
foo.cc:8:17: note: ‘b’ was declared here
    8 |         int a=n,b,r;
      |                 ^