diff --git a/bangdori/268.js b/bangdori/268.js
new file mode 100644
index 0000000..177907d
--- /dev/null
+++ b/bangdori/268.js
@@ -0,0 +1,11 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var missingNumber = function (nums) {
+  const n = nums.length;
+  const original = (n * (n + 1)) / 2;
+  const result = nums.reduce((acc, curr) => acc + curr, 0);
+
+  return original - result;
+};