Given two sorted linked lists, write a function to merge them into one?

list* merge(LIST* list1, LIST* list2){
LIST *it1, *it2, *head;
if(!list1) return list2;
if(!list2) return list1;
head = (list1->value <= list2->value) ? list1 : list2;
if(head == list1)
{ it1 = list1; it2 = list2;
}
else{
it1 = list2;
it2 = list1;
}
while(it1->next && it2){
if(it1->next->value >= it2->value){
list *temp = it1->next;
it1->next = it2;
it2 = it2->next;
it1->next->next = temp;
}
else{
it1 = it1->next;
}
}

if(it2)
it1->next = it2;
return head;
}