foo.cc: In function 'int cmp(const node&, const node&)':
foo.cc:69:18: warning: self-comparison always evaluates to false [-Wtautological-compare]
   69 |     return L.val < L.val;
      |            ~~~~~ ^ ~~~~~
foo.cc: In function 'void init()':
foo.cc:75:33: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   75 |     for (int i=1;i<=n;i++) scanf("%d",&a[i].val), a[i].pos=i;
      |                            ~~~~~^~~~~~~~~~~~~~~~
foo.cc:76:33: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   76 |     for (int i=1;i<=n;i++) scanf("%d",&b[i]);
      |                            ~~~~~^~~~~~~~~~~~

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