diff --git a/doitchuu/ContainsDuplicate.js b/doitchuu/ContainsDuplicate.js
new file mode 100644
index 0000000..62dce10
--- /dev/null
+++ b/doitchuu/ContainsDuplicate.js
@@ -0,0 +1,10 @@
+/**
+ * @param {number[]} nums
+ * @return {boolean}
+ */
+var containsDuplicate = function(nums) {
+    const arrLength = nums.length;
+    const set = new Set(nums);
+
+    return arrLength !== set.size;
+};
diff --git a/doitchuu/RomanToInteger.js b/doitchuu/RomanToInteger.js
new file mode 100644
index 0000000..a28e8f2
--- /dev/null
+++ b/doitchuu/RomanToInteger.js
@@ -0,0 +1,29 @@
+/**
+ * @param {string} s
+ * @return {number}
+ */
+var romanToInt = function(s) {
+    const romanMap = {
+        "I": 1,
+        "V": 5,
+        "X": 10,
+        "L": 50,
+        "C": 100,
+        "D": 500,
+        "M": 1000
+    };
+    let sum = 0;
+
+    for (let i = 0; i < s.length - 1; i++) {
+        const current = romanMap[s[i]];
+        const next = romanMap[s[i + 1]];
+
+        if (current < next) {
+            sum -= current;
+        } else {
+            sum += current;
+        }
+    }
+
+    return sum += romanMap[s[s.length - 1]];
+};