C# Sharepoint Library access removal error

Question

I need to remove all the unique permissions in Library level example "Documents"

path:https://sites.xxx.com/sites/11111/_layouts/15/User.aspx?List=

The following code throws error.

Could you please help me?

class Program
    {
        static void Main(string[] args)
        {
            ClientContext ctx = new ClientContext(<siteUrl>);
            var username = "Rajkumar P"; // This user needs to be removed
            Web wsite = ctx.Web;
            ctx.Load(wsite, w => w.HasUniqueRoleAssignments, w => w.RoleAssignments.Include(roleAssigned => roleAssigned.Member.Title,
                roleAssigned => roleAssigned.RoleDefinitionBindings.Include(roleDef => roleDef.Name)));
            ctx.ExecuteQuery();
            RoleAssignment ra = wsite.RoleAssignments.Where(r => r.Member.Title.Equals(username)).FirstOrDefault();
            ra.DeleteObject();
            wsite.Update();

            SecureString secureString = new SecureString();
            string password = "password";
            foreach (char c in password.ToCharArray()) secureString.AppendChar(c);

            NetworkCredential myCred = new NetworkCredential(
                    "<userntid>", secureString,"<FQDN>");
            ctx.Credentials = myCred;
            ctx.ExecuteQuery();

        }
    }

Error:

Exception thrown: 'Microsoft.SharePoint.Client.ServerUnauthorizedAccessException' in Microsoft.SharePoint.Client.Runtime.dll
An unhandled exception of type 'Microsoft.SharePoint.Client.ServerUnauthorizedAccessException' occurred in Microsoft.SharePoint.Client.Runtime.dll
Access denied. You do not have permission to perform this action or access this resource.