diff --git a/g0rnn/README.md b/g0rnn/README.md
index c0d0128..f49870e 100644
--- a/g0rnn/README.md
+++ b/g0rnn/README.md
@@ -34,5 +34,6 @@
 | 30차시 | 2025.07.28 | segment-tree | [커피숍2](https://www.acmicpc.net/problem/1275) | https://github.com/AlgoLeadMe/AlgoLeadMe-12/pull/121 |
 | 31차시 | 2025.08.03 | segment-tree | [음주코딩](https://www.acmicpc.net/problem/5676) | https://github.com/AlgoLeadMe/AlgoLeadMe-12/pull/127 |
 | 32차시 | 2025.08.09 | topology-sort | [문제집](https://www.acmicpc.net/problem/1766) | https://github.com/AlgoLeadMe/AlgoLeadMe-12/pull/128 |
+| 33차시 | 2025.08.21 | tree | [트리의 지름](https://www.acmicpc.net/problem/1167) | https://github.com/AlgoLeadMe/AlgoLeadMe-12/pull/134 |
 
 ---
diff --git "a/g0rnn/\355\212\270\353\246\254/33-g0rnn.java" "b/g0rnn/\355\212\270\353\246\254/33-g0rnn.java"
new file mode 100644
index 0000000..2aa5b3b
--- /dev/null
+++ "b/g0rnn/\355\212\270\353\246\254/33-g0rnn.java"
@@ -0,0 +1,54 @@
+package beakjoon;
+
+import java.io.*;
+import java.util.*;
+
+public class Sol1167 {
+
+    static int v;
+    static List<List<int[]>> tree = new ArrayList<>();
+    static int endNode, max = -1;
+    static boolean[] visited;
+
+    public static void main(String[] args) throws IOException {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        v = Integer.parseInt(br.readLine());
+        for (int i = 0; i <= v; i++) {
+            tree.add(new ArrayList<>());
+        }
+        for (int i = 0; i < v; i++) {
+            StringTokenizer st = new StringTokenizer(br.readLine());
+            int cur = Integer.parseInt(st.nextToken());
+            while (true) {
+                int u = Integer.parseInt(st.nextToken());
+                if (u == -1) break;
+                int cost = Integer.parseInt(st.nextToken());
+                tree.get(cur).add(new int[]{u, cost});
+            }
+        }
+        br.close();
+
+        visited = new boolean[v + 1];
+        //visited[0] = true;
+        dfs(1, 0);
+
+        visited = new boolean[v + 1];
+        //visited[endNode] = true;
+        //max = -1;
+        dfs(endNode, 0);
+
+        System.out.println(max);
+    }
+
+    private static void dfs(int node, int len) {
+        if (len > max) {
+            max = len;
+            endNode = node;
+        }
+        visited[node] = true;
+        for (int[] next : tree.get(node)) {
+            if (visited[next[0]]) continue;
+            dfs(next[0], len + next[1]);
+        }
+    }
+}