queue Array in C

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

#define max 5

void insert(int) ;
void display() ;
int del() ;
int queue[max] ;
int front = -1 ;
int rear = -1 ;

int main() {
    int option , num ;
 while(1)   
 {
  printf("\n 1 to insert , \n 2 to delete , \n 3 to display , \n 4 to exit ") ;
  scanf("%d" , &option) ;
  switch(option) {
     
      case 1:
             printf("\n Input a number\n ") ;
             scanf("%d" , &num) ;
             insert(num) ;
             break ;
            
      case 2:
             num = del() ;
             break ;
            
      case 3:
            display() ;
            break ;
           
      case 4: 
            exit(1) ;
           
      default: printf("\n fuck") ;
                   
    }
    
    
    
 }
   
   
   
   
   
    return 0 ;
}

void insert(int element) {
   
 if (rear == max-1 ) {
  printf("\n queue is full") ;
  return ; 
 }

 if(front == -1) {
  front = 0 ;  
    
 }
 rear = rear + 1 ;
 queue[rear] = element ;
   
   
}

int del() {
    int element ;
 if (front == -1 || front == rear + 1) {
  printf("\n queue is empty ") ;
  return ;
 }
 element = queue[front] ;
 front = front + 1 ;

 printf("%d is deleted " , element) ;
 return element ;

   
}
void display() {
   
  if (front == -1 || front == rear + 1) {
  printf("\n queue is empty ") ;
  return ;
 } 
 
  int i ;
 
  for(i=front ; i <=rear ; i++) {
   printf("\n %d , " , queue[i]) ;  
     
  }
   
}