foo.cc: In function 'int main()':
foo.cc:7:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &n, &m);
  ~~~~~^~~~~~~~~~~~~~~~~
foo.cc:9:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &num[i]);
   ~~~~~^~~~~~~~~~~~~~~
foo.cc:12:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d", &opt);
   ~~~~~^~~~~~~~~~~~
foo.cc:14:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d %d %d", &l, &r, &v);
    ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:21:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d %d", &l, &r);
    ~~~~~^~~~~~~~~~~~~~~~~

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