foo.cc: In function 'int solve(int, int, int)':
foo.cc:12:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i=0;i<v[idx].size();i++)
               ~^~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:24:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d",&n,&m);
  ~~~~~^~~~~~~~~~~~~~
foo.cc:28:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d%d",&l,&r,&x);
   ~~~~~^~~~~~~~~~~~~~~~~~~

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