понятно?

using System;
using System.IO;
using System.Linq;
using System.Collections.Generic;
namespace Example
{

    struct Spoint
    {
        public int x, y, z;

        public static Spoint Get(string points)
        {
            string[] s = points.Split();
            Spoint cur = new Spoint();
            cur.x = Int32.Parse(s[0]);
            cur.y = Int32.Parse(s[1]);
            cur.z = Int32.Parse(s[2]);
            return cur;
        }
        static int sqr(int x)
        {
            return x * x;
        }

        public static double Range(Spoint a, Spoint b)
        {
            return Math.Sqrt(sqr(a.x - b.x) + sqr(a.y - b.y) + sqr(a.z - b.z));
        }

        public override string ToString()
        {
            return x.ToString() + " " + y.ToString() + " " + z.ToString();
        }

    }


    class Program
    {

        static (Spoint, Spoint) Solve(Spoint[] p)
        {
            int fs, sc;
            fs = sc = 0;
            double ans = Double.MaxValue;
            for (int i = 0; i < p.Length; i++)
            {

                for (int j = 0; j < p.Length; j++)
                {
                    if (i == j)
                    continue;
                    double cur = Spoint.Range(p[i], p[j]);
                    if (cur < ans)
                    {
                        ans = cur;
                        fs = i;
                        sc = j;
                    }
                }
            }
            return (p[fs], p[sc]);
        }

        static void Main()
        {
            string[] inpLine = null;
            using (StreamReader inFile = new StreamReader("D:/input.txt"))
            {
                 inpLine = inFile.ReadToEnd().Split('\n');
            }
            Spoint[] points = new Spoint[inpLine.Length];
            for (int i = 0; i < points.Length; i++)
            {
                points[i] = Spoint.Get(inpLine[i]);
            }

            var ans = Solve(points);
            Console.WriteLine(ans.Item1);
            Console.WriteLine(ans.Item2);

            Console.ReadKey();
        }
    }
}