package main

type ListNode struct {
	Val  int
	Next *ListNode
}

func main() {

}

func swapPairs(head *ListNode) *ListNode {

	firstNode := (*ListNode)(head)
	secondNode := (*ListNode)(nil)
	num := 0
	for head != nil {
		if head.Next != nil {
			if head.Next.Next != nil {
				if num == 0 {
					firstNode = head.Next
					secondNode = head
				}
				if secondNode != nil && num != 0 {
					secondNode.Next = head.Next
				}
				tmpright := head.Next.Next
				head.Next.Next = head
				head.Next = tmpright
				secondNode = head
				head = tmpright

				num++
				continue
			} else {
				if num == 0 {
					firstNode = head.Next
					secondNode = head
				}
				if secondNode != nil && num != 0 {
					secondNode.Next = head.Next
				}
				tmpright := head.Next.Next
				head.Next.Next = head
				secondNode = head
				head.Next = tmpright

			}
		}
		head = head.Next
		num++
	}
	return firstNode
}