diff --git a/best-time-to-buy-and-sell-stock/RiaOh.js b/best-time-to-buy-and-sell-stock/RiaOh.js
new file mode 100644
index 000000000..74cff4c7e
--- /dev/null
+++ b/best-time-to-buy-and-sell-stock/RiaOh.js
@@ -0,0 +1,15 @@
+/**
+ * @param {number[]} prices
+ * @return {number}
+ */
+var maxProfit = function (prices) {
+  // 가장 작은 수
+  let minNum = prices[0];
+  // 차이 값
+  let maxProfit = 0;
+  for (let i = 1; i < prices.length; i++) {
+    minNum = Math.min(minNum, prices[i - 1]); // 이전꺼 중 가장 작은 수
+    maxProfit = Math.max(maxProfit, prices[i] - minNum);
+  }
+  return maxProfit;
+};
diff --git a/container-with-most-water/RiaOh.js b/container-with-most-water/RiaOh.js
new file mode 100644
index 000000000..9ab83a9f4
--- /dev/null
+++ b/container-with-most-water/RiaOh.js
@@ -0,0 +1,24 @@
+/**
+ * @param {number[]} height
+ * @return {number}
+ */
+const maxArea = function (height) {
+  let left = 0;
+  let right = height.length - 1;
+  let max = 0;
+
+  while (left < right) {
+    const graphW = right - left;
+    const grapghH = Math.min(height[left], height[right]);
+
+    max = Math.max(max, graphW * grapghH);
+
+    if (height[left] <= height[right]) {
+      left++;
+    } else {
+      right--;
+    }
+  }
+
+  return max;
+};
diff --git a/valid-parentheses/RiaOh.js b/valid-parentheses/RiaOh.js
new file mode 100644
index 000000000..6549c6c7d
--- /dev/null
+++ b/valid-parentheses/RiaOh.js
@@ -0,0 +1,28 @@
+/**
+ * @param {string} s
+ * @return {boolean}
+ */
+var isValid = function (s) {
+  const newArr = [...s];
+  if (newArr[0] === ")" || newArr[0] === "}" || newArr[0] === "]") {
+    return false;
+  }
+
+  for (let i = 1; i < newArr.length; i++) {
+    if (newArr[i] === ")" && newArr[i - 1] === "(") {
+      newArr.splice(i - 1, 2);
+      i = i - 2;
+    }
+
+    if (newArr[i] === "}" && newArr[i - 1] === "{") {
+      newArr.splice(i - 1, 2);
+      i = i - 2;
+    }
+
+    if (newArr[i] === "]" && newArr[i - 1] === "[") {
+      newArr.splice(i - 1, 2);
+      i = i - 2;
+    }
+  }
+  return newArr.length === 0 ? true : false;
+};