/in/foo.cc:34:19: error: 'maxn' was not declared in this scope
 void dfs(int tree[maxn], int s, int d, int res)
                   ^~~~
/in/foo.cc:34:24: error: expected ')' before ',' token
 void dfs(int tree[maxn], int s, int d, int res)
                        ^
/in/foo.cc:34:26: error: expected unqualified-id before 'int'
 void dfs(int tree[maxn], int s, int d, int res)
                          ^~~