diff --git a/InSange/BFS/310_Minimum Height Trees.cpp b/InSange/BFS/310_Minimum Height Trees.cpp
new file mode 100644
index 0000000..d482392
--- /dev/null
+++ b/InSange/BFS/310_Minimum Height Trees.cpp	
@@ -0,0 +1,66 @@
+#include <vector>
+#include <map>
+#include <queue>
+
+using namespace std;
+
+class Solution {
+public:
+    vector<int> findMinHeightTrees(int n, vector<vector<int>>& edges) {
+        map<int, vector<int>> m;
+        vector<int> ans;
+        vector<bool> check(n, false);
+        int* degree = new int[n] {0};
+
+        for (vector<int> node : edges)
+        {
+            m[node[0]].push_back(node[1]);
+            m[node[1]].push_back(node[0]);
+            degree[node[0]]++;
+            degree[node[1]]++;
+        }
+        int current_n = n;
+
+        queue<int> q;
+        if (current_n > 2)
+        {
+            for (int i = 0; i < n; i++)
+            {
+                if (degree[i] == 1 && check[i] == false)
+                {
+                    check[i] = true;
+                    q.push(i);
+                    current_n--;
+                }
+            }
+        }
+        while (current_n > 2 && !q.empty())
+        {
+            int size = q.size();
+
+            for (int j = 0; j < size; j++)
+            {
+                int remove_n = q.front();
+                q.pop();
+
+                for (auto node : m[remove_n])
+                {
+                    degree[node]--;
+                    if (degree[node] == 1)
+                    {
+                        q.push(node);
+                        check[node] = true;
+                        current_n--;
+                    }
+                }
+            }
+        }
+
+        for (int i = 0; i < n; i++)
+        {
+            if (check[i] == false) ans.push_back(i);
+        }
+
+        return ans;
+    }
+};
\ No newline at end of file
diff --git a/InSange/README.md b/InSange/README.md
index 537b1a9..6e73fbf 100644
--- a/InSange/README.md
+++ b/InSange/README.md
@@ -26,6 +26,9 @@
 | 22차시 | 2024.07.31 |  DP  | [Filling Bookcase Shelves](https://leetcode.com/problems/filling-bookcase-shelves/)  | [#22](https://github.com/AlgoLeadMe/AlgoLeadMe-8/pull/81)]
 | 23차시 | 2024.08.03 |  슬라이딩 윈도우  | [Minimum Swaps to Group All 1's Together 2](https://leetcode.com/problems/minimum-swaps-to-group-all-1s-together-ii/)  | [#23](https://github.com/AlgoLeadMe/AlgoLeadMe-8/pull/82)]
 | 24차시 | 2024.08.04 |  BFS  | [트리](https://www.acmicpc.net/problem/1068)  | [#24](https://github.com/AlgoLeadMe/AlgoLeadMe-8/pull/83)]
+| 25차시 | 2024.08.10 |  BFS  | [Minimum Height Trees](https://leetcode.com/problems/minimum-height-trees/)  | [#25](https://github.com/AlgoLeadMe/AlgoLeadMe-8/pull/87)]
+| 26차시 | 2024.08.11 |  수학  | [Magic Squares In Grid](https://leetcode.com/problems/magic-squares-in-grid/)  | [#26](https://github.com/AlgoLeadMe/AlgoLeadMe-8/pull/89)]
+| 27차시 | 2024.08.17 |  문자열  | [Number of Senior Citizens](https://leetcode.com/problems/number-of-senior-citizens/)  | [#27](https://github.com/AlgoLeadMe/AlgoLeadMe-8/pull/91)]
 ---
 
 https://leetcode.com/problems/robot-collisions/
diff --git "a/InSange/\353\254\270\354\236\220\354\227\264/2678_Number of Senior Citizens.cpp" "b/InSange/\353\254\270\354\236\220\354\227\264/2678_Number of Senior Citizens.cpp"
new file mode 100644
index 0000000..656e589
--- /dev/null
+++ "b/InSange/\353\254\270\354\236\220\354\227\264/2678_Number of Senior Citizens.cpp"	
@@ -0,0 +1,24 @@
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+class Solution {
+public:
+    int countSeniors(vector<string>& details) {
+        int seniorCount = 0;
+
+        for (string& passengerInfo : details) {
+            int ageTens = passengerInfo[11] - '0';
+            int ageOnes = passengerInfo[12] - '0';
+
+            int age = ageTens * 10 + ageOnes;
+
+            if (age > 60) {
+                seniorCount++;
+            }
+        }
+
+        return seniorCount;
+    }
+};
\ No newline at end of file
diff --git "a/InSange/\354\210\230\355\225\231/840_Magic Squares In Grid.cpp" "b/InSange/\354\210\230\355\225\231/840_Magic Squares In Grid.cpp"
new file mode 100644
index 0000000..f830c03
--- /dev/null
+++ "b/InSange/\354\210\230\355\225\231/840_Magic Squares In Grid.cpp"	
@@ -0,0 +1,55 @@
+#include <vector>
+
+using namespace std;
+
+class Solution {
+public:
+    bool Check(int r, int c, vector<vector<int>>& grid)
+    {
+        vector<bool> isCheck(10, false);
+
+        for (int i = 0; i < 3; i++)
+        {
+            for (int j = 0; j < 3; j++)
+            {
+                int num = grid[r + i][c + j];
+                if (num < 1 || num > 9) return false;
+                if (isCheck[num]) return false;
+                isCheck[num] = true;
+            }
+        }
+
+        int standard_num = grid[r][c] + grid[r + 1][c + 1] + grid[r + 2][c + 2];
+        if (standard_num != grid[r][c + 2] + grid[r + 1][c + 1] + grid[r + 2][c]) return false;
+
+        for (int i = 0; i < 3; i++)
+        {
+            if (standard_num != (grid[r + i][c] + grid[r + i][c + 1] + grid[r + i][c + 2])) return false;
+        }
+
+        for (int i = 0; i < 3; i++)
+        {
+            if (standard_num != (grid[r][c + i] + grid[r + 1][c + i] + grid[r + 2][c + i])) return false;
+        }
+
+        return true;
+    }
+
+    int numMagicSquaresInside(vector<vector<int>>& grid) {
+        int col = grid[0].size(), row = grid.size();
+
+        if (col < 3 || row < 3) return 0;
+
+        int ans = 0;
+
+        for (int i = 0; i < row - 2; i++)
+        {
+            for (int j = 0; j < col - 2; j++)
+            {
+                if (Check(i, j, grid)) ans++;
+            }
+        }
+
+        return ans;
+    }
+};
\ No newline at end of file