diff --git a/flydongwoo/AlgoLeadMe_Week23_prob01.cpp b/flydongwoo/AlgoLeadMe_Week23_prob01.cpp
new file mode 100644
index 0000000..907aedc
--- /dev/null
+++ b/flydongwoo/AlgoLeadMe_Week23_prob01.cpp
@@ -0,0 +1,111 @@
+#include <iostream>
+#include <vector>
+#include <numeric>
+
+using namespace std;
+
+int R, C, T;
+vector<vector<int>> room;
+int purifier_top_r = -1;
+int purifier_bottom_r = -1;
+
+int dr[] = { 0, 1, 0, -1 };
+int dc[] = { 1, 0, -1, 0 };
+
+void spread_dust() {
+    vector<vector<int>> diffused_dust(R, vector<int>(C, 0));
+
+    for (int r = 0; r < R; r++) {
+        for (int c = 0; c < C; c++) {
+            if (room[r][c] > 0) {
+                int spread_amount = room[r][c] / 5;
+                int spread_count = 0;
+
+                for (int i = 0; i < 4; i++) {
+                    int nr = r + dr[i];
+                    int nc = c + dc[i];
+
+                    if (nr >= 0 && nr < R && nc >= 0 && nc < C && room[nr][nc] != -1) {
+                        diffused_dust[nr][nc] += spread_amount;
+                        spread_count++;
+                    }
+                }
+                room[r][c] -= spread_amount * spread_count;
+            }
+        }
+    }
+
+    for (int r = 0; r < R; r++) {
+        for (int c = 0; c < C; c++) {
+            room[r][c] += diffused_dust[r][c];
+        }
+    }
+}
+
+void circulate_air() {
+    for (int r = purifier_top_r - 1; r > 0; r--) {
+        room[r][0] = room[r - 1][0];
+    }
+    for (int c = 0; c < C - 1; c++) {
+        room[0][c] = room[0][c + 1];
+    }
+    for (int r = 0; r < purifier_top_r; r++) {
+        room[r][C - 1] = room[r + 1][C - 1];
+    }
+    for (int c = C - 1; c > 1; c--) {
+        room[purifier_top_r][c] = room[purifier_top_r][c - 1];
+    }
+    room[purifier_top_r][1] = 0;
+
+    for (int r = purifier_bottom_r + 1; r < R - 1; r++) {
+        room[r][0] = room[r + 1][0];
+    }
+    for (int c = 0; c < C - 1; c++) {
+        room[R - 1][c] = room[R - 1][c + 1];
+    }
+    for (int r = R - 1; r > purifier_bottom_r; r--) {
+        room[r][C - 1] = room[r - 1][C - 1];
+    }
+    for (int c = C - 1; c > 1; c--) {
+        room[purifier_bottom_r][c] = room[purifier_bottom_r][c - 1];
+    }
+    room[purifier_bottom_r][1] = 0;
+}
+
+int main() {
+    ios_base::sync_with_stdio(false);
+    cin.tie(NULL);
+
+    cin >> R >> C >> T;
+    room.resize(R, vector<int>(C));
+
+    for (int i = 0; i < R; i++) {
+        for (int j = 0; j < C; j++) {
+            cin >> room[i][j];
+            if (room[i][j] == -1) {
+                if (purifier_top_r == -1) {
+                    purifier_top_r = i;
+                    purifier_bottom_r = i + 1;
+                }
+            }
+        }
+    }
+
+    while (T--) {
+        spread_dust();
+        circulate_air();
+    }
+
+    int total_dust = 0;
+    for (int i = 0; i < R; i++) {
+        for (int j = 0; j < C; j++) {
+            if (room[i][j] > 0) {
+                total_dust += room[i][j];
+            }
+        }
+    }
+
+    cout << total_dust << endl;
+
+    return 0;
+}
\ No newline at end of file
diff --git a/flydongwoo/README.md b/flydongwoo/README.md
index da77089..5f1de2d 100644
--- a/flydongwoo/README.md
+++ b/flydongwoo/README.md
@@ -21,4 +21,7 @@
 | 17차시 | 2025.08.06 |  DFS와 BFS  | [바이러스](https://www.acmicpc.net/problem/2606)|https://github.com/AlgoLeadMe/AlgoLeadMe-15/pull/63|
 | 18차시 | 2025.08.07 |  BFS  | [숨바꼭질](https://www.acmicpc.net/problem/1697)|https://github.com/AlgoLeadMe/AlgoLeadMe-15/pull/64|
 | 19차시 | 2025.08.14 |  Sliding Window  | [수열](https://www.acmicpc.net/problem/2559)|https://github.com/AlgoLeadMe/AlgoLeadMe-15/pull/71|
-
+| 20차시 | 2025.08.27 |  Greedy Algorithm  | [ATM](https://www.acmicpc.net/problem/11399)|https://github.com/AlgoLeadMe/AlgoLeadMe-15/pull/81|
+| 21차시 | 2025.08.28 |  BFS  | [토마토](https://www.acmicpc.net/problem/7576)|https://github.com/AlgoLeadMe/AlgoLeadMe-15/pull/82|
+| 22차시 | 2025.09.05 |  시뮬레이션  | [로봇 청소기](https://www.acmicpc.net/problem/14503)|https://github.com/AlgoLeadMe/AlgoLeadMe-15/pull/87|
+| 23차시 | 2025.09.06 |  시뮬레이션  | [미세먼지 안녕!](https://www.acmicpc.net/problem/17144)|https://github.com/AlgoLeadMe/AlgoLeadMe-15/pull/88|