diff --git a/S2OJ/2021/2021.cpp b/S2OJ/2021/2021.cpp
new file mode 100644
index 00000000..fdf20623
--- /dev/null
+++ b/S2OJ/2021/2021.cpp
@@ -0,0 +1,52 @@
+#include <iostream>
+
+using std::cin;
+using std::cout;
+const char endl = '\n';
+
+const int N = 35;
+
+int n, f[N][N], root[N][N];
+
+void dfs(int l, int r) {
+    if (l > r) return;
+
+    cout << root[l][r] << ' ';
+
+    if (l == r) return;
+    dfs(l, root[l][r] - 1);
+    dfs(root[l][r] + 1, r);
+}
+
+int main() {
+    std::ios::sync_with_stdio(false);
+
+    cin >> n;
+    for (int i = 1; i <= n; i++) {
+        cin >> f[i][i];
+        f[i][i - 1] = 1;
+        root[i][i] = i;
+    }
+
+    for (int len = 2; len <= n; len++) {
+        for (int l = 1, r = len; r <= n; l++, r++) {
+            f[l][r] = f[l][l] + f[l + 1][r];
+            root[l][r] = l;
+
+            for (int k = l + 1; k < r; k++) {
+                if (f[l][r] < f[l][k - 1] * f[k + 1][r] + f[k][k]) {
+                    f[l][r] = f[l][k - 1] * f[k + 1][r] + f[k][k];
+                    root[l][r] = k;
+                }
+            }
+        }
+    }
+
+    cout << f[1][n] << endl;
+
+    dfs(1, n);
+
+    cout << endl;
+
+    return 0;
+}
diff --git a/S2OJ/2021/data/binary1.in b/S2OJ/2021/data/binary1.in
new file mode 100644
index 00000000..9d4f854b
--- /dev/null
+++ b/S2OJ/2021/data/binary1.in
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:4bcf7edfdf9c633a7f14fd2c0cf33aceb0e7e72d7974b9cefacf0d27461b9d87
+size 14
diff --git a/S2OJ/2021/data/binary1.out b/S2OJ/2021/data/binary1.out
new file mode 100644
index 00000000..c3311138
--- /dev/null
+++ b/S2OJ/2021/data/binary1.out
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:b12d9851aef9160b9c6906c34cfe7df631b44b5432a95297cc6ecc89b6c50975
+size 14
diff --git a/S2OJ/2021/data/binary2.in b/S2OJ/2021/data/binary2.in
new file mode 100644
index 00000000..22f5a344
--- /dev/null
+++ b/S2OJ/2021/data/binary2.in
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:43764ea63e4d55b63710e487ba4f07a886e05eae2e74a5ec572e13c5f09f89fe
+size 27
diff --git a/S2OJ/2021/data/binary2.out b/S2OJ/2021/data/binary2.out
new file mode 100644
index 00000000..1f72e15a
--- /dev/null
+++ b/S2OJ/2021/data/binary2.out
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:93ac18d8e3b2cd94fc707b3a34660933f503296788b35ac28a2aa270c8596ce1
+size 28
diff --git a/S2OJ/2021/data/binary3.in b/S2OJ/2021/data/binary3.in
new file mode 100644
index 00000000..a65f622e
--- /dev/null
+++ b/S2OJ/2021/data/binary3.in
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:dc23b74d609a1bed01f3c1c2fe2de5ee21acb2cf4bdc076a8d92696db78ada71
+size 36
diff --git a/S2OJ/2021/data/binary3.out b/S2OJ/2021/data/binary3.out
new file mode 100644
index 00000000..7666d889
--- /dev/null
+++ b/S2OJ/2021/data/binary3.out
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:cb9a15fc253492d19bcd400bdb5ad9a9a746e324f3ac6ce8ad70f7c53aa21fda
+size 44
diff --git a/S2OJ/2021/data/binary4.in b/S2OJ/2021/data/binary4.in
new file mode 100644
index 00000000..a53c181b
--- /dev/null
+++ b/S2OJ/2021/data/binary4.in
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:1a4d6d928d22749ee4b0a61c6919ef901a4b5f5b24fe473962372cbce4643c30
+size 46
diff --git a/S2OJ/2021/data/binary4.out b/S2OJ/2021/data/binary4.out
new file mode 100644
index 00000000..f7e07503
--- /dev/null
+++ b/S2OJ/2021/data/binary4.out
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:0a6df54873fdd44d88d3950b67e7f1b8dc022c1531b9d5819944359293e04ea7
+size 61
diff --git a/S2OJ/2021/data/binary5.in b/S2OJ/2021/data/binary5.in
new file mode 100644
index 00000000..4533a593
--- /dev/null
+++ b/S2OJ/2021/data/binary5.in
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:29d5ae8a88b6f215cbd9a1ef24736adecfeeb7a2394acace7945d4043cc4adc7
+size 53
diff --git a/S2OJ/2021/data/binary5.out b/S2OJ/2021/data/binary5.out
new file mode 100644
index 00000000..81d53c59
--- /dev/null
+++ b/S2OJ/2021/data/binary5.out
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:e31ad175dd5e14a1ee4d7afc5d0f385653a0d724e7f07733550167f20670f29e
+size 76
diff --git a/S2OJ/2021/data/chk.cpp b/S2OJ/2021/data/chk.cpp
new file mode 100644
index 00000000..677d7ab2
--- /dev/null
+++ b/S2OJ/2021/data/chk.cpp
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:791abe35039dbc43477c77585e5e14367ab22b3de7de15f1f0ed419776f70e10
+size 1506
diff --git a/S2OJ/2021/data/problem.conf b/S2OJ/2021/data/problem.conf
new file mode 100644
index 00000000..0b16e5e0
--- /dev/null
+++ b/S2OJ/2021/data/problem.conf
@@ -0,0 +1,3 @@
+version https://git-lfs.github.com/spec/v1
+oid sha256:2e617960f3c55b7ae31aff48975b8bf919b191c72fa1057aed4cc87fc7b5e154
+size 210