diff --git a/YIM2UL2ET/README.md b/YIM2UL2ET/README.md
index 81be847..5a91848 100644
--- a/YIM2UL2ET/README.md
+++ b/YIM2UL2ET/README.md
@@ -2,5 +2,7 @@
 
 | 차시 |    날짜    | 문제유형 | 링크 | 풀이 |
 |:----:|:---------:|:----:|:-----:|:----:|
-| 1차시 | 2023.10.27 |  그리디  | [BOJ 18310](https://www.acmicpc.net/problem/18310)  | [BOJ 18310 풀이](https://github.com/AlgoLeadMe/AlgoLeadMe-7/pull/3) |
+| 1차시 | 2024.02.12 |  그리디  | [BOJ 18310](https://www.acmicpc.net/problem/18310)  | [BOJ 18310 풀이](https://github.com/AlgoLeadMe/AlgoLeadMe-7/pull/3) |
+| 2차시 | 2024.02.15 |  그리디  | [BOJ 1263](https://www.acmicpc.net/problem/1263)  | [BOJ 1449 풀이](https://github.com/AlgoLeadMe/AlgoLeadMe-7/pull/7) |
+| 3차시 | 2024.02.18 |  자료구조  | [BOJ 2504](https://www.acmicpc.net/problem/2504)  | [BOJ 2504 풀이](https://github.com/AlgoLeadMe/AlgoLeadMe-7/pull/9) |
 ---
diff --git "a/YIM2UL2ET/\352\267\270\353\246\254\353\224\224/2\354\260\250\354\213\234- BOJ 1263 .cpp" "b/YIM2UL2ET/\352\267\270\353\246\254\353\224\224/2\354\260\250\354\213\234- BOJ 1263 .cpp"
new file mode 100644
index 0000000..fe2c22f
--- /dev/null
+++ "b/YIM2UL2ET/\352\267\270\353\246\254\353\224\224/2\354\260\250\354\213\234- BOJ 1263 .cpp"	
@@ -0,0 +1,41 @@
+#include <iostream>
+#include <algorithm>
+#include <vector>
+
+bool compare(std::vector <int> &vec1, std::vector <int> &vec2);
+
+int main(void)
+{
+    int n, result, end_time;
+    std::cin >> n;
+
+    std::vector <std::vector <int>> vec(n);
+    for (int i = 0; i < n; i++) {
+        int t, s;
+        std::cin >> t >> s;
+        vec[i].push_back(t);
+        vec[i].push_back(s);
+    }
+
+    std::sort(vec.begin(), vec.end(), compare);
+
+    result = vec[0][1] - vec[0][0], end_time = vec[0][1];
+    for (int i = 1; i < n; i++) {
+        if (end_time + vec[i][0] > vec[i][1]) {
+            result -= end_time + vec[i][0] - vec[i][1];
+            end_time = vec[i][1];
+        }
+        else end_time += vec[i][0];
+    }
+
+    if (result < 0) std::cout << "-1";
+    else std::cout << result;
+    
+    return 0;
+}
+
+bool compare(std::vector <int> &vec1, std::vector <int> &vec2)
+{
+    if (vec1[1] == vec2[1]) return vec1[0] < vec2[0];   
+    else return vec1[1] < vec2[1];
+}
\ No newline at end of file
diff --git "a/YIM2UL2ET/\354\212\244\355\203\235/3\354\260\250\354\213\234 - BOJ 2504.cpp" "b/YIM2UL2ET/\354\212\244\355\203\235/3\354\260\250\354\213\234 - BOJ 2504.cpp"
new file mode 100644
index 0000000..af345fa
--- /dev/null
+++ "b/YIM2UL2ET/\354\212\244\355\203\235/3\354\260\250\354\213\234 - BOJ 2504.cpp"	
@@ -0,0 +1,41 @@
+#include <iostream>
+#include <stack>
+#include <vector>
+
+int main(void)
+{
+    bool is_Cstr = true;
+    std::string str;
+    std::stack <char> stk;
+    std::vector <int> vec;
+
+    std::cin >> str;
+
+    for (int i = 0; i < str.size(); i++) {
+        if (str[i] == '(' || str[i] == '[') {
+            stk.push(str[i]);
+            if (stk.size() > vec.size()) vec.push_back(0);
+        }
+        else if (!stk.empty() && ((str[i] == ')' && stk.top() == '(') || (str[i] == ']' && stk.top() == '['))){
+            int value;
+            if (stk.top() == '(') value = 2;
+            else value = 3;
+
+            if (stk.size() < vec.size()) {
+                vec[vec.size()-2] += vec.back() * value;
+                vec.pop_back();
+            }
+            else vec[vec.size()-1] += value;
+
+            stk.pop();
+        }
+        else {
+            is_Cstr = false;
+            break;
+        }
+    }
+
+    if (!is_Cstr || !stk.empty()) std::cout << 0;
+    else std::cout << vec[0];
+    return 0;
+}
\ No newline at end of file