diff --git a/khj20006/202603/26 BOJ P5 LCS 4.md b/khj20006/202603/26 BOJ P5 LCS 4.md
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+```java
+import java.io.*;
+import java.util.*;
+
+public class BOJ13711 {
+    static class SegmentTree {
+        int[] tree;
+        SegmentTree(int size) {
+            tree = new int[size*4];
+        }
+
+        void update(int s, int e, int i, int v, int n) {
+            if(s == e) {
+                tree[n] = v;
+                return;
+            }
+            int m = (s+e)>>1;
+            if(i <= m)  update(s, m, i, v, n*2);
+            else        update(m+1, e, i, v, n*2+1);
+            tree[n] = Math.max(tree[n*2], tree[n*2+1]);
+        }
+
+        int find(int s, int e, int l, int r, int n) {
+            if(l>r || l>e || r<s) return 0;
+            if(l<=s && e<=r) return tree[n];
+            int m = (s+e)>>1;
+            return Math.max(find(s, m, l, r, n*2), find(m+1, e, l, r, n*2+1));
+        }
+    }
+
+    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+    static BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+    static StringTokenizer st;
+
+    static int N;
+    static int[] index;
+    static SegmentTree seg;
+
+    public static void main(String[] args) throws Exception {
+        N = Integer.parseInt(br.readLine());
+
+        index = new int[N+1];
+        st = new StringTokenizer(br.readLine());
+        for(int i=1;i<=N;i++) {
+            index[Integer.parseInt(st.nextToken())] = i;
+        }
+
+        seg = new SegmentTree(N);
+        st = new StringTokenizer(br.readLine());
+        for(int i=1;i<=N;i++) {
+            int a = Integer.parseInt(st.nextToken());
+            int val = seg.find(1, N, 1, index[a], 1) + 1;
+            seg.update(1, N, index[a], val, 1);
+        }
+
+        bw.write(seg.tree[1] + "\n");
+        bw.close();
+    }
+}
+```