diff --git a/C#/the-number-of-beautiful-subsets.cs b/C#/the-number-of-beautiful-subsets.cs
new file mode 100644
index 0000000..1222808
--- /dev/null
+++ b/C#/the-number-of-beautiful-subsets.cs
@@ -0,0 +1,38 @@
+/**
+ * time O(n)
+ * space O(n)
+ */
+
+public class Solution {
+    public int BeautifulSubsets(int[] nums, int k) {
+        Dictionary<int, int> cnt = new Dictionary<int, int>();
+        foreach (int x in nums) {
+            if (cnt.ContainsKey(x)) {
+                cnt[x]++;
+            } else {
+                cnt[x] = 1;
+            }
+        }
+
+        Func<int, int> count = (int x) => {
+            int y = x;
+            while (cnt.ContainsKey(y - k)) {
+                y -= k;
+            }
+            List<int> dp = new List<int> { 1, 0 };
+            for (int i = y; i <= x; i += k) {
+                dp = new List<int> { dp[0] + dp[1], dp[0] * ((1 << cnt[i]) - 1) };
+            }
+            return dp[0] + dp[1];
+        };
+
+        int result = 1;
+        foreach (var kvp in cnt) {
+            int i = kvp.Key;
+            if (!cnt.ContainsKey(i + k)) {
+                result *= count(i);
+            }
+        }
+        return result - 1;
+    }
+}