foo.c: In function ‘main’:
foo.c:16:136: error: ‘bs’ undeclared (first use in this function); did you mean ‘ys’?
   16 |                         if (((a[i] - xs == 1 || a[i] - xs == -1) && (b[i] - ys == 0 || b[i] - ys == 2 || b[i] - ys == -2)) || ((b[i] - bs == 1 || b[i] - ys == -1) && (a[i] - xs == 0 || a[i] - xs == 2 || a[i] - xs == -2)))
      |                                                                                                                                        ^~
      |                                                                                                                                        ys
foo.c:16:136: note: each undeclared identifier is reported only once for each function it appears in