diff --git a/sik9252/ ContainsDuplicate.js b/sik9252/ ContainsDuplicate.js
new file mode 100644
index 0000000..f3e3122
--- /dev/null
+++ b/sik9252/ ContainsDuplicate.js	
@@ -0,0 +1,4 @@
+var containsDuplicate = function (nums) {
+  const removeDuplicate = new Set(nums);
+  return nums.length === removeDuplicate.size ? false : true;
+};
diff --git a/sik9252/ RomanToInteger.js b/sik9252/ RomanToInteger.js
new file mode 100644
index 0000000..feba44a
--- /dev/null
+++ b/sik9252/ RomanToInteger.js	
@@ -0,0 +1,26 @@
+var romanToInt = function (s) {
+  const map = {
+    I: 1,
+    V: 5,
+    X: 10,
+    L: 50,
+    C: 100,
+    D: 500,
+    M: 1000,
+  };
+
+  let result = 0;
+
+  for (let i = 0; i < s.length; i++) {
+    const current = map[s[i]];
+    const next = map[s[i + 1]];
+
+    if (current < next) {
+      result -= current;
+    } else {
+      result += current;
+    }
+  }
+
+  return result;
+};