foo.cc: In function 'void scan()':
foo.cc:10:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   10 |             scanf("%d", &a[i][j]);
      |             ~~~~~^~~~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:31:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   31 |     scanf("%d%d", &n, &m);
      |     ~~~~~^~~~~~~~~~~~~~~~

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