foo.cc: In function 'int main()':
foo.cc:80:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &n);
  ~~~~~^~~~~~~~~~
foo.cc:82:35: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for(int i = 1; i <= n; ++i) scanf("%d%d", &xx1[i], &yy1[i]);
                              ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:83:35: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  for(int i = 1; i <= n; ++i) scanf("%d%d", &xx2[i], &yy2[i]);
                              ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

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