queue in c array

//Queue Implemented in array
// C-Program

#include<stdio.h>
#include<malloc.h>
#include<stdlib.h>

void insert(int *ar,int *front,int *rear,int N){
        int n;
        printf("Enter number to insert :");
        scanf("%d",&n);

        if((*front==0 && *rear== N) || *front==*rear+1){
            printf("overflow condition -> queue is full");
        }
        else if(*front==-1){
            *front=0;
            *rear=0;
            *(ar+(*rear))=n;
        }
        else if(*rear==N && *front !=0){
            *rear=0;
            *(ar+(*rear))=n;
        }
        else{
            *rear=*rear+1;
            *(ar+(*rear))=n;
        }
}
int del(int *ar,int *front,int *rear,int N){
    int x;
       if(*front == -1 ){   //queue is empty
        printf("\nUnderflow cond! -> No element in queue to delete");
       }
       else if(*front==*rear){ //only one element in queue
            x=*(ar+(*front));
            *front=-1;
            *rear=-1;
       }
       else if(*front ==N){
        x=*(ar+(*front));
        *front=0;
       }
       else{
        x=*(ar+(*front));
        *front=*front+1;
       }
       return x;

}
void display(int *ar,int f,int r,int N){
    printf("\n");
    if(f<=r){
        while(f<=r){
            printf(" %d ",*(ar+f));
            f=f+1;
        }
    }
    else{
        while(f<=N){
            printf(" %d ",*(ar+f));
            f=f+1;
        }
        f=0;
        while(f<=r){
            printf(" %d ",*(ar+f));
            f=f+1;
        }
    }
    printf("\n");
}

main(){
    int maxsi,front=-1,rear=-1;
    int ch,x;
    int *ar;
    printf("Enter Max size of Queue : ");
    scanf("%d",&maxsi);   // max number of element you wanna put in queue

    ar=(int*)malloc(sizeof(int)*maxsi); //create array of size maxsi

    while(1){
        printf(" 1 : Insert \n 2 : Delete \n 3 : Exit\n  Enter your choice :");
        scanf("%d",&ch);
        switch(ch){
            case 1:

                insert(ar,&front,&rear,maxsi-1);
                display(ar,front,rear,maxsi-1);
                break;
            case 2:
                x=del(ar,&front,&rear,maxsi-1);
                printf("\n%d is deleted from queue",x);
                display(ar,front,rear,maxsi-1);
                break;
            case 3:
                exit(0);
                break;
            default:
                printf("Wrong choice try again ??");
                break;
        }
    }
}