程序设计作业的一个问题，有关链表和指针（已解决）

已给出主函数和fun.c，要设计函数

#include <stdio.h>
#include "fun.h"

int main(void) {
    int n, num;
    scanf("%d", &n);

    struct Node* head = NULL;
    while (n--) {
        scanf("%d", &num);
        insert(&head, num);
    }
    print_linklist(head);
    delete_linklist(head);
}

#include <stdlib.h> 
struct Node {
    struct Node* next;
    int value;
};

void insert(struct Node** head, int num);

void print_linklist(struct Node* head);

void delete_linklist(struct Node* head);

以下是我写的函数的设计

#include <stdlib.h> 
#include <stdio.h>
#include "fun.h"

void insert(struct Node** head, int num)
{
    struct Node *l;
    struct Node *p;
    l = *head;
    if(l -> next == NULL) （在这里提示出了问题）
    {
        l -> next -> value = num;
    }
    else
    {
        if(num >= l -> value)
        {
            l = l -> next;
            l -> value = num;
        }
        else
        {
            p = *head;
            while(num > p -> next -> value)
            {
                p = p -> next;
            }
            struct Node *m;
            struct Node *n;
            n = p -> next;
            m = p;
            m -> next -> value = num;
            m -> next -> next = n;
        }
    }
}

void print_linklist(struct Node* head)
{
    while(head -> next != NULL)
    {
        printf("%d", head -> next -> value);
    }
}

void delete_linklist(struct Node* head)
{
    struct Node *l;
    while(head -> next != NULL)
    {
        l = head -> next;
        free(head);
        head = l;
    }
}

出了一些问题，搞了好久还是不知道为什么，请教一下各位大神！