diff --git a/AcWing/789/789.cpp b/AcWing/789/789.cpp
new file mode 100644
index 00000000..3fc8fd50
--- /dev/null
+++ b/AcWing/789/789.cpp
@@ -0,0 +1,42 @@
+#include <bits/stdc++.h>
+
+using namespace std;
+
+int n, q, t, k, a[100005];
+
+int main() {
+    cin >> n >> q;
+    for (int i = 0; i < n; i++) {
+        cin >> a[i];
+    }
+    for (int i = 0; i < q; i++) {
+        cin >> k;
+        int l = 0;
+        int r = n - 1;
+        while (l < r) {
+            int mid = l + r >> 1;
+            if (a[mid] >= k) {
+                r = mid;
+            } else {
+                l = mid + 1;
+            }
+        }
+        if (a[l] != k) {
+            cout << -1 << ' ' << -1 << endl;
+            continue;
+        }
+        cout << l << ' ';
+        l = 0;
+        r = n - 1;
+        while (l < r) {
+            int mid = l + r + 1 >> 1;
+            if (a[mid] <= k) {
+                l = mid;
+            } else {
+                r = mid - 1;
+            }
+        }
+        cout << l << endl;
+    }
+    return 0;
+}