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Given an integer S. Find the largest even number that can be formed by rearranging the digits of S.

**Note:** In case the number does not contain any even digit then output the largest odd number possible.

**Example 1:**

**Input:**
S = "1324"
**Output:** "4312"
**Explanation:** Largest even number: 4312

Example 2:

**Input:**
S = "3555"
**Output:** "5553"
**Explanation:** No even number possible,
So we'll find largest odd number.

**Your Task: **

You don't need to read input or print anything. Your task is to complete the function **LargestEven()** which takes the string **S **as inputs representing the integer and returns the answer.

**Expected Time Complexity:** O(|S| * log |S|)

**Expected Auxiliary Space:** O(1)

**Constraints:**

1 ≤ **|S|** ≤ 10^{5}

**S** contains only digits from '0' to '9'.

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Largest Even Number

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