Operations on a Linked List

#include <stdio.h>
#include <stdlib.h>
struct node{
    int data;
    struct node* next;
}*headA = NULL;
void display(struct node* help){
    if(!help) printf(" Empty!");
    while(help){
        printf(" %d ", help->data);
        help = help->next;
    }
}
struct node* insert(int value, struct node*help){
    struct node *newNode = (struct node*) malloc(sizeof(newNode));
    newNode->data = value; newNode->next = NULL;
    if(help) newNode->next = help;
    help = newNode;
    display(help);
    return help;
}
struct node* input(struct node *head){
    int n;
    while(1){
        printf("\nInput(-1 to stop): ");
        scanf("%d",&n);
        if(n!=-1) head = insert(n, head);
        else return head;
    }
}
void copy(struct node* help){
    struct node *headB = NULL, *last = NULL;
    while(help){
        struct node *newNode = (struct node*) malloc(sizeof(struct node));
        newNode->data = help->data; newNode->next = NULL;
        if(!headB){
            headB = newNode;
            last = newNode;
        } else{
            last->next = newNode;
            last = last->next;
        }
        help = help->next;
    }
    help = last = NULL;
    free(help); free(last);
    printf("\nThe copied linked list is:");
    display(headB); free(headB);
}
void concatenate(struct node *help){
    struct node *headB = NULL;
    printf("\nEnter elements for the second Linked List\n");
    headB = input(headB);
    if(!help) headA = headB;
    while(help->next) help = help->next;
    help->next = headB;
    printf("\nTwo linked lists have been concatenated:");
    display(headA);
    headB = NULL; free(headB);
}
void split(struct node *help, int index){
    for(int i = 0; i < index; i++) help = help->next;
    struct node *headB = help->next;
    help->next = NULL;
    printf("\nThe first linked list:"); display(headA);
    printf("\nThe second linked list:"); display(headB); free(headB);
}
void reverse(struct node* help){
    struct node *forward = headA, *back = NULL;
    while (forward){
        help = forward;
        forward = help->next;
        help->next = back;
        back = help;
    }
    headA = back;
    back = forward = help = NULL;
    free(back); free(forward); free(help);
    printf("\nThe linked list has been reversed:");
    display(headA);
}
int count(struct node* help){
    int count = 0;
    while(help){
        count++;
        help = help->next;
    }
    return count;
}
int main(){
    int n;
    printf("\nEnter elements for first Linked List.\n");
    headA = input(headA);
    while(1){
        printf("\n1.Copy 2.Concatenate 3.Split 4.Reverse 5.Count 6.Exit: ");
        scanf("%d",&n);
        switch(n){
            case 1: copy(headA); break;
            case 2: concatenate(headA); break;
            case 3: split(headA,count(headA)/2-1); break;
            case 4: reverse(headA); break;
            case 5: printf("\nThe number of nodes are %d.", count(headA)); break;
            case 6: return 0;
            default: printf("\nEnter a number between 1 and 6.");
        }
    }
}