foo.cc: In function 'void work()':
foo.cc:71:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   71 |     scanf("%d%d", &n, &m);
      |     ~~~~~^~~~~~~~~~~~~~~~
foo.cc:72:39: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   72 |     for (int i = 1; i <= n; i++) scanf("%d", &k[i]);
      |                                  ~~~~~^~~~~~~~~~~~~
foo.cc:74:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   74 |     scanf("%d%d", &u, &v); add(v, u); kp[u]++;
      |     ~~~~~^~~~~~~~~~~~~~~~

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