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", &n, &m);
  ^~~~~~~~~~~~~~~~~~~~~~
foo.c:9:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &num[i]);
   ^~~~~~~~~~~~~~~~~~~~
foo.c:12:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &opt);
   ^~~~~~~~~~~~~~~~~
foo.c:14:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d %d %d", &l, &r, &v);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:21:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d %d", &l, &r);
    ^~~~~~~~~~~~~~~~~~~~~~

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