using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace retrun
{
    class Program
    {
        static void Main(string[] args)
        {
            string act = Console.ReadLine();
            string rev = "";
            for (int index = act.Length-1;index >= 0;index--)
            {
                rev += act[index];
            }
            Console.WriteLine("{0}",rev);
            Console.ReadKey();
        }
    }
}

网页题目：C#倒序输出字符
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