foo.cc: In function 'int bfs_1(int)':
foo.cc:31:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |         for (int i=1;i<a[now].size();i++)
      |                      ~^~~~~~~~~~~~~~
foo.cc:32:16: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
   32 |             if (del[a[now][i]]==0)
      |                ^

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