First_non_repeating_number

arr = [2, 3, 4, 2, 3, 5]

def first_non_repeating(inp):
    count = {}

    # First pass: count frequency
    for i in inp:
        count[i] = count.get(i, 0) + 1

    # Second pass: find first non-repeating
    for i in inp:
        if count[i] == 1:
            return i

    return None
    

print(first_non_repeating(arr))