C++ program queue

#include <iostream>

using namespace std;
int queue[100], n = 100, front = - 1, rear = - 1;
void Insert() {
   int val;
   if (rear == n - 1)
   cout<<"Queue Overflow";
   else {
      if (front == - 1)
      front = 0;
      cout<<"Insert the element in queue : ";
      cin>>val;
      rear++;
      queue[rear] = val;
   }
}
void Delete() {
   if (front == - 1 || front == rear) {
      cout<<"Queue Underflow ";
      return ;
   } else {
      cout<<"Element deleted from queue is : "<< queue[front];
      front++;;
   }
}
void Display() {
   if (front == - 1)
   cout<<"Queue is empty";
   else {
      cout<<"Queue elements are : ";
      for (int i = front; i <= rear; i++)
      cout<<queue[i]<<" ";
        
   }
}
int main() {
   int ch;
   cout<<"1. Insert element to queue\n";
   cout<<"2. Delete element from queue\n";
   cout<<"3. Display all the elements of queue\n";
   cout<<"4. Exit\n";
   do {
      cout<<"Enter your choice : ";
      cin>>ch;
      switch (ch) {
         case 1: Insert();
         break;
         case 2: Delete();
         break;
         case 3: Display();
         break;
         case 4: cout<<"Exit";
         break;
         default: cout<<"Invalid choice";
      }
   } while(ch!=4);
   return 0;
}