Next greater element 2

public class Solution {
    public int[] NextGreaterElements(int[] nums) {
        
    int l = nums.Length;
        
    int[] arr = new int[2*l];
    
    arr = nums.Concat(nums).ToArray();
        
     int l1 = arr.Length;
        
     int[] ans = new int[l1];
     var st = new Stack<int>(){};
        
        
     for(int i =0;i<l1;i++)
     {
         while(st.Count!=0 && arr[i]>arr[st.Peek()])
         {
             ans[st.Peek()] = arr[i];
             st.Pop();
         }
         
         st.Push(i);
         
     }
        
         while(st.Count!=0)
         {
         ans[st.Peek()]=-1;
         st.Pop();
         }
     
        
    var list = new List<int>(){};
    for(int k=0;k<l1/2;k++)
    {
        list.Add(ans[k]);
    }
    
        return list.ToArray();
        //return arr;
        
        
    }
}