foo.c: In function 'main':
foo.c:6:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &n, &m);
     ^~~~~~~~~~~~~~~~~~~~~
foo.c:8:9: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d", &num[i]);
         ^~~~~~~~~~~~~~~~~~~~
foo.c:11:9: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d", &opt);
         ^~~~~~~~~~~~~~~~~
foo.c:13:13: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%d%d%d", &l, &r, &v);
             ^~~~~~~~~~~~~~~~~~~~~~~~~~~
foo.c:20:13: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
             scanf("%d%d", &l, &r);
             ^~~~~~~~~~~~~~~~~~~~~

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