foo.cc: In function ‘int main()’:
foo.cc:12:33: error: ‘b’ was not declared in this scope
   12 |                                 b+=1;
      |                                 ^
foo.cc:14:33: error: ‘b’ was not declared in this scope
   14 |                                 b+=0;
      |                                 ^
foo.cc:15:20: error: ‘b’ was not declared in this scope
   15 |                 if(b==n-2)
      |                    ^