diff --git a/AcWing/253/253.cpp b/AcWing/253/253.cpp
new file mode 100644
index 00000000..508debb2
--- /dev/null
+++ b/AcWing/253/253.cpp
@@ -0,0 +1,26 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int main() {
+    int n, x, opt;
+    vector<int> a;
+    cin >> n;
+    for (int i = 0; i < n; i++) {
+        cin >> opt >> x;
+        if (opt == 1) {
+            a.insert(lower_bound(a.begin(), a.end(), x), x);
+        } else if (opt == 2) {
+            a.erase(lower_bound(a.begin(), a.end(), x));
+        } else if (opt == 3) {
+            cout << lower_bound(a.begin(), a.end(), x) - a.begin() + 1 << endl;
+        } else if (opt == 4) {
+            cout << a[x - 1] << endl;
+        } else if (opt == 5) {
+            cout << *--lower_bound(a.begin(), a.end(), x) << endl;
+        } else if (opt == 6) {
+            cout << *upper_bound(a.begin(), a.end(), x) << endl;
+        }
+    }
+    return 0;
+}
\ No newline at end of file