Problem:
Score : 100 points

Problem Statement

You are given four digits N_1, N_2, N_3 and N_4. Determine if these can be arranged into the sequence of digits "1974".

Constraints

0 \leq N_1, N_2, N_3, N_4 \leq 9

N_1, N_2, N_3 and N_4 are integers.

Input

Input is given from Standard Input in the following format:

N_1 N_2 N_3 N_4

Output

If N_1, N_2, N_3 and N_4 can be arranged into the sequence of digits "1974", print YES; if they cannot, print NO.

Sample Input 1

1 7 9 4

Sample Output 1

YES

We can get 1974 by swapping N_2 and N_3.

Sample Input 2

1 9 7 4

Sample Output 2

YES

We already have 1974 before doing anything.

Sample Input 3

1 2 9 1

Sample Output 3

NO

Sample Input 4

4 9 0 8

Sample Output 4

NO

Solution in C# (Mono 4.6.2.0) (judge verdict: Accepted)

using System;

class AtCoder
{
    static void Main()
    {
        string[] s;       
        s = NextS();
        int[] a = new int[4];
        for (int i = 0; i < 4; i++) a[i] = int.Parse(s[i]);
        Array.Sort(a);
        if (a[0] == 1 && a[1] == 4 && a[2] == 7 && a[3] == 9)
            Console.WriteLine("YES");
        else Console.WriteLine("NO");
    }

    static void DebugWL(object x) { System.Diagnostics.Debug.WriteLine(x); }
    static string[] NextS() { return Console.ReadLine().Trim().Split(' '); }
}