diff --git "a/lkhyun/202503/19 BOJ \352\263\250\353\223\2341 \352\265\254\352\260\204\355\225\251 \352\265\254\355\225\230\352\270\260.md" "b/lkhyun/202503/19 BOJ \352\263\250\353\223\2341 \352\265\254\352\260\204\355\225\251 \352\265\254\355\225\230\352\270\260.md"
new file mode 100644
index 00000000..0988391b
--- /dev/null
+++ "b/lkhyun/202503/19 BOJ \352\263\250\353\223\2341 \352\265\254\352\260\204\355\225\251 \352\265\254\355\225\230\352\270\260.md"	
@@ -0,0 +1,68 @@
+```java
+import java.util.*;
+import java.io.*;
+
+public class Main {
+    static int N;
+    static int M;
+    static int K;
+    static long[] arr;
+    static long[] tree;
+    public static void main(String[] args) throws Exception {
+        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+        StringTokenizer st = new StringTokenizer(br.readLine());
+        N = Integer.parseInt(st.nextToken());
+        M = Integer.parseInt(st.nextToken());
+        K = Integer.parseInt(st.nextToken());
+        arr = new long[N*4];
+        tree = new long[N*4];
+        
+        for(int i=1;i<=N;i++){
+            arr[i] = Long.parseLong(br.readLine());
+        }
+        init(1,1,N);
+        for(int i=0;i<M+K;i++){
+            st = new StringTokenizer(br.readLine());
+            int option = Integer.parseInt(st.nextToken());
+            int arg1 = Integer.parseInt(st.nextToken());
+            long arg2 = Long.parseLong(st.nextToken());
+            if(option == 1){//수정
+                update(1,1,N,arg1,arg2-arr[arg1]);
+                arr[arg1] = arg2;
+            }else if(option == 2){//구간 합
+                bw.write(query(1,1,N,arg1,(int)arg2) + "\n");
+            }
+        }
+        bw.close();
+    }
+    public static void init(int num, int start, int end){ //초기화하는 거
+        if(start==end){
+            tree[num] = arr[start];
+        }else{
+            init(num*2, start, (start+end)/2);
+            init(num*2 + 1,(start+end)/2 + 1, end);
+            tree[num] = tree[num*2] + tree[num*2+1];
+        }
+    }
+    public static long query(int num, int start, int end, int left, int right){ //구간 합
+        if(right<start || left>end){//구하려는 구간내에 현재 범위가 없어.
+            return 0;
+        }else if(left<=start && right>=end){//구하려는 구간내에 현재 범위가 있어. 다 더해야겟지
+            return tree[num];
+        }
+        long lsum = query(num*2, start, (start+end)/2, left, right);
+        long rsum = query(num*2+1, (start+end)/2 + 1, end, left, right);
+        return lsum + rsum;
+    }
+    public static void update(int num, int start, int end, int index, long diff){// 수정
+        if(start>index || end<index) return; //현재 위치가 수정할 곳과 연관이 있는가?
+        tree[num] += diff; // 있으니 변화량 반영
+
+        if(start != end){//현재 위치가 리프노드인가? 그렇다면 이미 반영이 되었고 아니라면 재귀적으로 반영해야함.
+            update(num*2, start,(start+end)/2,index,diff);
+            update(num*2+1,(start+end)/2 + 1,end,index,diff);
+        }
+    }
+}
+```