/in/foo.cc: In function 'int main()':
/in/foo.cc:14:10: error: 'i' was not declared in this scope
     for (i=2+N;i<=2*N+1;i++)    board[i]='B';
          ^
/in/foo.cc:15:10: error: 'i' was not declared in this scope
     for (i=1;i<=M;i++)
          ^
/in/foo.cc:41:10: error: 'i' was not declared in this scope
     for (i=1;i<=2*N+1;i++)  cout<<board[i];
          ^