Cannot implicity convert int to int[]

Question

Hey, i am new to this forum(first question here).

 

So Here my problem is that i have this code and the last return statement it says "cannot implicitly convert int to int[]".

 

Earlier i did a few tweaks to code but no luck can't find the solution! 

 

Now here's the code 

using System;

public class Program
{
    public static void Main()
    {
        Console.WriteLine(FindDuplicates([1,2,2,3]));
    }

    public int[] FindDuplicates(int[] nums)
    {
        var tortoise = nums[0];
        var hare = nums[0];
        while(true)
        {
            tortoise = nums[tortoise];
            hare = nums[nums[hare]];
            if(tortoise == hare)
                break;
        }

        var ptr1 = nums[0];
        var ptr2 = nums[tortoise];

        while(ptr1 != ptr2)
        {
            ptr1 = nums[ptr1];
            ptr2 = nums[ptr2];
        }

        return ptr1;
    }
}