foo.c: In function 'main':
foo.c:21:9: warning: statement with no effect [-Wunused-value]
   21 |         for (x; x < m; x++)
      |         ^~~
foo.c:36:9: warning: statement with no effect [-Wunused-value]
   36 |         for (y; y < n; y++)
      |         ^~~

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