/in/foo.cc: In function 'int main()':
/in/foo.cc:25:2: warning: this 'for' clause does not guard... [-Wmisleading-indentation]
  for(int k=2;k<=n;k++)
  ^~~
/in/foo.cc:38:3: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'for'
   printf("%d\n",f[1][n]);printf("%d",root[1][n]);pre_dfs(1,root[1][n]-1);pre_dfs(root[1][n]+1,n);return 0;
   ^~~~~~