Insert at first singly

 #include<stdio.h>
 #include<stdlib.h>
 typedef struct node
 {
     int a;
     struct node *next;
 }node;

 node *head=NULL;

 void insert_at_first()
 {
     node *N=(node*)malloc(sizeof(node));
     scanf("%d", &N->a);
     N->next=NULL;

     if (head==NULL)
     {
         head=N;
         return;
     }
     else
     {
        N->next=head;
        head=N;
        return;
     }
 }

 void display()
{
    node *list=head;
    while(list!=NULL)
    {
        printf("%d\n", list->a);
        list=list->next;
    }
}

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

     for(i=0; i<n; i++)
     {
         insert_at_first();
     }
     display();
 }