using System;
using System.Text;

public class Test
{
    private static string FindLcs(string s, string t) {
        var L = new int[s.Length, t.Length];
        var z = 0;
        var ret = new StringBuilder();
        for (var i = 0 ; i != s.Length ; i++) {
            for (var j = 0 ; j != t.Length ; j++) {
                if (s[i] == t[j]) {
                    if (i == 0 || j == 0) {
                        L[i,j] = 1;
                    } else {
                        L[i,j] = L[i-1,j-1] + 1;
                    }
                    if (L[i,j] > z) {
                        z = L[i,j];
                        ret = new StringBuilder();
                    }
                    if (L[i,j] == z) {
                        ret.Append(s.Substring( i-z+1, z));
                    }
                } else {
                    L[i,j]=0;
                }
            }
        }
        return ret.ToString();
    }
    private static string CutLcs(string s, string t) {
        for (;;) {
            var lcs = FindLcs(s, t);
            if (lcs.Length < 10) break;
            s = s.Replace(lcs, string.Format("[{0}]", lcs.Length));
        }
        return s;
    }

	public static void Main()
	{
    string firstS = "/9j/4AAQSkZJRgABAQEAYABgAAD/2wBDABQODxIPDRQSERIXFhQYHzMhHxwcHz8tLyUzSkFOTUlBSEZSXHZkUldvWEZIZoxob3p9hIWET2ORm4+AmnaBhH//2wBDARYXFx8bHzwhITx/VEhUf39/f39/f39/f39/f39/f39/f39/f39/f39/f39/f39/f39/f39/f39/f39/f39/f3//";
    string secondS = "abcdefg2wBDABQODxIPDRQSERIXFh/f39/f39/f39/f39/f39/f39/f39/f39/f39/f39/f39/f39/f39/f39/f39/abcdefg";
    Console.WriteLine(CutLcs(firstS, secondS));
	}
}