foo.c: In function 'main':
foo.c:5:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld %lld %lld", &n, &m, &k);
  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:9:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%lld", &a[i][j]);
    ^~~~~~~~~~~~~~~~~~~~~~~
foo.c:14:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%lld", &b[i][j]);
    ^~~~~~~~~~~~~~~~~~~~~~~

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