foo.cc: In function 'void dfs(int, int)':
foo.cc:18:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   18 |     for (int i = 0; i < p[pos].size(); i++)
      |                     ~~^~~~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:39:23: warning: statement has no effect [-Wunused-value]
   39 |                 flag2 == 1;
      |                 ~~~~~~^~~~

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