diff --git a/Codeforce/ECF101/A.cpp b/Codeforce/ECF101/A.cpp
new file mode 100644
index 0000000..24a1348
--- /dev/null
+++ b/Codeforce/ECF101/A.cpp
@@ -0,0 +1,27 @@
+#include <iostream>
+#include <queue>
+#include <stack>
+#include <vector>
+using namespace std;
+class Solution {
+ public:
+  bool PossibleRBS(string s) {// is possible to obtain RBS !
+    if ((s.size() % 2 == 1) || s.back() == '(' || s.front() == ')') {
+      return false;
+    } else {
+      return true;
+    }
+  }
+};
+int main() {
+  int T;
+  cin >> T;
+  Solution Instance;
+  string s;
+  while (T--) {
+    cin >> s;
+    cout << (Instance.PossibleRBS(s) ? "YES" : "NO") << endl;
+  }
+
+  return 0;
+}
\ No newline at end of file
diff --git a/Codeforce/ECF101/B.cpp b/Codeforce/ECF101/B.cpp
new file mode 100644
index 0000000..3951a2f
--- /dev/null
+++ b/Codeforce/ECF101/B.cpp
@@ -0,0 +1,77 @@
+#include <algorithm>
+#include <iostream>
+#include <numeric>
+#include <vector>
+
+using namespace std;
+string path = "/Users/hakunamatata/CLionProjects/Foxconn/Codeforce/";
+const int INF = 0x3F3F3F3F;
+
+class Solution {
+  // T: O(N*M)
+ public:
+  int solve(vector<int> p, vector<int> q) {
+    int n = p.size(), m = q.size();
+    vector<vector<int>> dp(n + 1, vector<int>(m + 1, -INF));
+    dp[0][0] = 0;
+    int ans = 0;
+    for (int i = 0; i <= n; i++) {
+      for (int j = 0; j <= m; j++) {
+        if (i < n) dp[i + 1][j] = max(dp[i + 1][j], dp[i][j] + p[i]);
+        if (j < m) dp[i][j + 1] = max(dp[i][j + 1], dp[i][j] + q[j]);
+        ans = max(ans, dp[i][j]);
+      }
+    }
+    return ans;
+  }
+  // T: O(N+M)
+  int solve_(vector<int> p, vector<int> q) {
+    partial_sum(p.begin(), p.end(), p.begin());
+    partial_sum(q.begin(), q.end(), q.begin());
+    return max(0, *max_element(p.begin(), p.end())) +max(0, *max_element(q.begin(), q.end()));
+  }
+  // error
+  int solve_err(vector<int> p, vector<int> q) {
+    int n = p.size(), m = q.size();
+    vector<vector<int>> dp(n + 1, vector<int>(m + 1, -INF));
+    // INIT
+    dp[0][0] = 0;
+    for (int i = 1; i <= m; i++) {
+      dp[0][i] = max(dp[0][i - 1], dp[0][i - 1] + q[i - 1]);
+    }
+    for (int i = 1; i <= n; i++) {
+      dp[i][0] = max(dp[i - 1][0], dp[i - 1][0] + p[i - 1]);
+    }
+    // tran
+    for (int i = 1; i < n + 1; i++) {
+      for (int j = 1; j < m + 1; j++) {
+        dp[i][j] = max(dp[i][j - 1], dp[i][j - 1] + q[j - 1]);
+        dp[i][j] = max(dp[i - 1][j], dp[i - 1][j] + p[i - 1]);
+      }
+    }
+    return dp[n][m];
+  }
+};
+// 测试数据
+int main() {
+  int T;
+  cin >> T;
+  Solution INSTANCE;
+  while (T--) {
+    int n, m, val;
+    vector<int> a, b;
+    cin >> n;
+    while (n--) {
+      cin >> val;
+      a.emplace_back(val);
+    }
+    cin >> m;
+    while (m--) {
+      cin >> val;
+      b.emplace_back(val);
+    }
+    int ans = INSTANCE.solve(a, b);
+    cout << ans << endl;
+  }
+  return 0;
+}
diff --git a/Codeforce/ECF101/B.txt b/Codeforce/ECF101/B.txt
new file mode 100644
index 0000000..bdb71da
--- /dev/null
+++ b/Codeforce/ECF101/B.txt
@@ -0,0 +1,5 @@
+1
+4
+6 -5 7 -3
+3
+2 3 -4