foo.cc: In function 'void dfs1(int, int)':
foo.cc:37:18: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   37 |      for(ri i=0;i<p[r].size();i++)
      |                 ~^~~~~~~~~~~~
foo.cc: In function 'void dfs2(int, int)':
foo.cc:63:17: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   63 |     for(ri i=0;i<p[r].size();i++)
      |                ~^~~~~~~~~~~~
foo.cc: In function 'void read()':
foo.cc:13:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   13 |     scanf("%d%d%d%lld",&n,&m,&R,&P);
      |     ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
foo.cc:16:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   16 |         scanf("%lld",&val[i]);
      |         ~~~~~^~~~~~~~~~~~~~~~
foo.cc:21:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   21 |         scanf("%d%d",&a,&b);
      |         ~~~~~^~~~~~~~~~~~~~
foo.cc: In function 'void solve()':
foo.cc:172:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  172 |         scanf("%d",&a);
      |         ~~~~~^~~~~~~~~
foo.cc:176:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  176 |             scanf("%d%d%d",&x,&y,&z);
      |             ~~~~~^~~~~~~~~~~~~~~~~~~
foo.cc:182:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  182 |             scanf("%d%d",&x,&y);
      |             ~~~~~^~~~~~~~~~~~~~
foo.cc:191:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  191 |             scanf("%d%d",&x,&z);
      |             ~~~~~^~~~~~~~~~~~~~
foo.cc:197:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  197 |             scanf("%d",&x);
      |             ~~~~~^~~~~~~~~

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Found 3 testcases.
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