How to find duplicates in Array for this particular code. C++

Question

I've been refreshing myself on arrays for once classes start. So for this I am given code and I need to be able to find duplicates in the user input. Any Solutions?

Ex: How it is: The numbers in reverse order is: 5 2 7 6 5 3 9

How it should be: The numbers in reverse order is: 2 7 6 5 3 9

note: The numbers are in reverse.

#include <iostream>
using namespace std;

const int ARRAY_SIZE = 1000;

int main()
{
    int count;
    int number;
    int numItems;
    int list[ARRAY_SIZE];

    count = 0;

    cout << "Enter a number (negative number to quit): ";
    cin >> number;
    while (number >= 0){
        list[count] = number;
        count++;
        cout << "Enter a number (negative number to quit): ";    
        cin >> number;
    }

    numItems = count;
    cout << "The numbers in reverse order is: ";
    for (count = numItems - 1; count >= 0; count--){
        cout << list[count] << " ";
    }
}