Equalize List Sums with Minimal Updates

You are given two lists of integers a and b where every element in both lists is between 1 to 6. Consider an operation where you pick a number in either a or b and update its value to a number between 1 to 6.

Return the minimum number of operations required such that the sum of a and b are equal. If it’s not possible, return -1.

Constraints

• n ≤ 100,000 where n is the length of a
• m ≤ 100,000 where m is the length of b

https://binarysearch.com/problems/Equalize-List-Sums-with-Minimal-Updates

Examples

Example 1

Input

• a = [1, 5]
• b = [6, 5, 5]

Output

• answer = 2

Explanation

If we change the 1 to 6 in a and the 6 to 1 in b, then both of their sums would be 11.

Example 2

Input

• a = [6]
• b = [1, 1, 1, 1, 1, 1, 1]

Output

• answer = -1

Explanation

There’s no way to make a and b’s sums equal.

Solution