foo.c: In function 'main':
foo.c:7:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&m,&n);
  ^~~~~~~~~~~~~~~~~~~
foo.c:10:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&a[i][j]);
    ^~~~~~~~~~~~~~~~~~~~

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