foo.cc: In function 'void dfs(int, int)':
foo.cc:22:8: warning: statement has no effect [-Wunused-value]
  for(it;it!=v[x].end();it++)
        ^
foo.cc: In function 'void dfs2(int, int)':
foo.cc:40:8: warning: statement has no effect [-Wunused-value]
  for(it;it!=v[x].end();it++)
        ^

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