/in/foo.cc: In function 'bool check(int)':
/in/foo.cc:5:26: error: 'n' was not declared in this scope
     for (int i = 0; i <= n; i++)
                          ^
/in/foo.cc:6:13: error: 'a' was not declared in this scope
         if((a[i] ^ x) > n)
             ^