Two strings - using C#, var, foreach, Any method - interesting to read

TwoStrings4.cs

using System;
using System.IO;
using System.Linq;

public class Solution
{
    static void Main()
    {
#if DEBUG
        Console.SetIn(File.OpenText("Input.txt"));
#endif
        var t = Convert.ToInt32(Console.ReadLine());
        for (var i = 0; i < t; i++)
        {
            var str1 = Console.ReadLine();
            var str2 = Console.ReadLine();
            var res = IsExistSubstring(str1, str2);
            Console.WriteLine(res);
        }
    }

    private static string IsExistSubstring(string str1, string str2)
    {
        const char start = 'a';

        var abc = new bool[26];
        foreach (var c in str1)
            abc[c - start] = true;

        return str2.Any(c => abc[c - start]) ? "YES" : "NO";
    }
}