foo.c: In function 'main':
foo.c:4:23: warning: unused variable 'min' [-Wunused-variable]
  int m, n, i, j, max, min, s = 0;
                       ^~~
foo.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &m, &n);
  ^~~~~~~~~~~~~~~~~~~~~~
foo.c:9:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d", &a[i][j]);
    ^~~~~~~~~~~~~~~~~~~~~

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