class Solution:
    def Merge(self, pHead1, pHead2):
        # write code here
        cur1,cur2=pHead1,pHead2
        '''极端情况'''
        if not cur1: return cur2
        elif not cur2: return cur1
        new_cur=ans=ListNode(0)
        while cur1 and cur2:
            if cur1.val<=cur2.val: 
                new_cur.next=cur1
                cur1=cur1.next
            else: 
                new_cur.next=cur2
                cur2=cur2.next
            new_cur=new_cur.next
        new_cur.next = cur1 if cur1 else cur2
        return ans.next