/in/foo.cc: In function 'int main()':
/in/foo.cc:29:33: error: 'flag' was not declared in this scope
   29 |                                 flag=0;
      |                                 ^~~~
/in/foo.cc:33:21: error: 'flag' was not declared in this scope
   33 |                 if (flag==1 && b[i]!=1)
      |                     ^~~~