foo.cc: In function 'int main()':
foo.cc:19:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   19 |  ll m, n, k;scanf("%lld%lld%lld", &m, &n, &k);
      |             ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~

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