using System;
using System.Globalization;
using System.Linq;
public class Program
{
public static void Main(string[] args)
{
int[] sequence = new[]{-10,17,13,17,-10,21};
var lowDup = sequence.GroupBy(i => i)
.OrderByDescending(g => g.Count())
.ThenBy(g => g.Key)
.First().Key;
Console.Write(lowDup);
}
}
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