diff --git a/README.en.md b/README.en.md
index ee554f418..af0c4f777 100644
--- a/README.en.md
+++ b/README.en.md
@@ -95,7 +95,7 @@ The data structures mainly include:
 
 ![198.house-robber](./assets/problems/198.house-robber.png)
 
-[0454.4-sum-ii](./problems/454.4-sum-ii.md):
+[0454.4-sum-ii](./problems/454.4-sum-ii.en.md) ✅:
 
 ![454.4-sum-ii](./assets/problems/454.4-sum-ii.png)
 
@@ -111,10 +111,6 @@ The data structures mainly include:
 
 > Here only lists some **representative problems** but not all.
 
-<<<<<<< HEAD
-
-=======
->>>>>>> upstream/master
 #### Easy (Translation in Progress)
 - [0001.TwoSum](./problems/1.TwoSum.en.md)🆕✅
 - [0020.Valid Parentheses](./problems/20.validParentheses.md)
@@ -174,11 +170,7 @@ The data structures mainly include:
 - [0062.unique-paths](./problems/62.unique-paths.md)
 - [0073.set-matrix-zeroes](./problems/73.set-matrix-zeroes.md)
 - [0075.sort-colors](./problems/75.sort-colors.md)
-<<<<<<< HEAD
-- [0078.subsets](./problems/78.subsets.md)
-=======
 - [0078.subsets](./problems/78.subsets-en.md)✅
->>>>>>> upstream/master
 - [0079.word-search](./problems/79.word-search-en.md) ✅
 - [0086.partition-list](./problems/86.partition-list.md)
 - [0090.subsets-ii](./problems/90.subsets-ii-en.md)✅
@@ -224,10 +216,7 @@ The data structures mainly include:
 - [0516.longest-palindromic-subsequence](./problems/516.longest-palindromic-subsequence.md)
 - [0518.coin-change-2](./problems/518.coin-change-2.md)
 - [0547.friend-circles](./problems/547.friend-circles-en.md) 🆕✅
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-=======
 - [0560.subarray-sum-equals-k](./problems/560.subarray-sum-equals-k.en.md) ✅
->>>>>>> upstream/master
 - [0609.find-duplicate-file-in-system](./problems/609.find-duplicate-file-in-system.md)
 - [0875.koko-eating-bananas](./problems/875.koko-eating-bananas.md)
 - [0877.stone-game](./problems/877.stone-game.md)
@@ -240,10 +229,6 @@ The data structures mainly include:
 - [1371.find-the-longest-substring-containing-vowels-in-even-counts](./problems/1371.find-the-longest-substring-containing-vowels-in-even-counts.en.md) 🆕✅
 
 
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-
-=======
->>>>>>> upstream/master
 #### Hard (Translation in Progress)
 
 - [0004.median-of-two-sorted-array](./problems/4.median-of-two-sorted-array.md) 🆕
diff --git a/problems/454.4-Sum-ii.en.md b/problems/454.4-Sum-ii.en.md
new file mode 100644
index 000000000..5a5d0eb82
--- /dev/null
+++ b/problems/454.4-Sum-ii.en.md
@@ -0,0 +1,100 @@
+
+
+## Problem Address
+https://leetcode.com/problems/4sum-ii/description/
+
+## Problem Description
+
+```
+Given four lists A, B, C, D of integer values, compute how many tuples (i, j, k, l) there are such that A[i] + B[j] + C[k] + D[l] is zero.
+
+To make problem a bit easier, all A, B, C, D have same length of N where 0 ≤ N ≤ 500. All integers are in the range of -228 to 228 - 1 and the result is guaranteed to be at most 231 - 1.
+
+Example:
+
+Input:
+A = [ 1, 2]
+B = [-2,-1]
+C = [-1, 2]
+D = [ 0, 2]
+
+Output:
+2
+
+Explanation:
+The two tuples are:
+1. (0, 0, 0, 1) -> A[0] + B[0] + C[0] + D[1] = 1 + (-2) + (-1) + 2 = 0
+2. (1, 1, 0, 0) -> A[1] + B[1] + C[0] + D[0] = 2 + (-1) + (-1) + 0 = 0
+```
+## Solution
+
+The normal solution to complete the search would require four rounds of traversal, and that would make the time complexity reaches O(n^4), which doesn't work obviously. We have to figure out a more effective algorithm.
+
+My idea is to separate these four lists into two groups and combine them two by two. We then calculate separately `all the sums from these two groups, and the relevant counts`
+
+As the picture shows:
+
+![454.4-sum-ii](../assets/problems/454.4-sum-ii.png)
+
+
+Now that we got two `hashTable`, and the result would appear with some basic calculations.
+
+## Key Point Analysis
+- Less time by more space.
+- Divide the lists by 2, and calculate all the possible sums from two groups, then combine the result.
+
+## Code
+
+Language Support: `JavaScript`，`Python3`
+
+`JavaScript`: 
+```js
+
+/*
+ * @lc app=leetcode id=454 lang=javascript
+ *
+ * [454] 4Sum II
+ *
+ * https://leetcode.com/problems/4sum-ii/description/
+/**
+ * @param {number[]} A
+ * @param {number[]} B
+ * @param {number[]} C
+ * @param {number[]} D
+ * @return {number}
+ */
+var fourSumCount = function(A, B, C, D) {
+  const sumMapper = {};
+  let res = 0;
+  for (let i = 0; i < A.length; i++) {
+    for (let j = 0; j < B.length; j++) {
+        sumMapper[A[i] + B[j]] = (sumMapper[A[i] + B[j]] || 0) + 1;
+    }
+  }
+
+  for (let i = 0; i < C.length; i++) {
+    for (let j = 0; j < D.length; j++) {
+        res += sumMapper[- (C[i] + D[j])] || 0;
+    }
+  }
+
+  return res;
+};
+```
+
+`Python3`: 
+
+```python
+class Solution:
+    def fourSumCount(self, A: List[int], B: List[int], C: List[int], D: List[int]) -> int:
+        mapper = {}
+        res = 0
+        for i in A:
+            for j in B:
+                mapper[i + j] = mapper.get(i + j, 0) + 1
+        
+        for i in C:
+            for j in D:
+                res += mapper.get(-1 * (i + j), 0)
+        return res
+ ```
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