diff --git a/bangdori/128.js b/bangdori/128.js
new file mode 100644
index 0000000..53d0e18
--- /dev/null
+++ b/bangdori/128.js
@@ -0,0 +1,32 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var longestConsecutive = function (nums) {
+  const set = new Set(nums);
+  const visited = new Set();
+  let answer = 0;
+  let count = 0;
+
+  const dfs = (num) => {
+    count++;
+    visited.add(num);
+
+    if (set.has(num + 1) && !visited.has(num + 1)) {
+      dfs(num + 1);
+    }
+
+    if (set.has(num - 1) && !visited.has(num - 1)) {
+      dfs(num - 1);
+    }
+  };
+
+  for (const num of set) {
+    if (visited.has(num)) continue;
+    count = 0;
+    dfs(num);
+    answer = Math.max(answer, count);
+  }
+
+  return answer;
+};