Pattern: 3 DSA + 18 -20 MCQS

You are given a binary array arr of size N, consisting only of 0s and 1s.

In one operation, you may flip any single element, i.e.:

• 0 → 1
• 1 → 0

Find the minimum number of flips required so that the number of 0s and 1s in the array becomes equal.

If it is impossible, print -1.

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Input Format

• The first line contains an integer N.
• The second line contains N space-separated integers (0 or 1).

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Output Format

Print a single integer representing the minimum number of flips required.

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Constraints

• (1 <= N <= 10^5)

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Example 1

Input

6
1 1 1 0 0 0

Output

0

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Example 2

Input

8
1 1 1 1 0 0 0 0

Output

0

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Example 3

Input

6
1 1 1 1 1 0

Output

2

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Example 4

Input

5
1 1 0 0 1

Output

-1