import java.util.Arrays;
import java.util.LinkedList;
import java.util.Scanner;

public class Main {
	
	public static long MOD = 1000000007;
	
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		final int v0 = sc.nextInt();
		final int v1 = sc.nextInt();
		final int v2 = sc.nextInt();
		final int v3 = sc.nextInt();
		
		final int INF = Integer.MAX_VALUE / 5 - 1;
		
		final int MAX = 30;
		int[] DP = new int[MAX + 1];
		
		int answer = INF;
		for(int a = 1; a <= MAX; a++){
			for(int b = a + 1; b <= MAX; b++){
				for(int c = b + 1; c <= MAX; c++){
					Arrays.fill(DP, INF);
					DP[0] = 0;
					
					for(int i = 0; i <= MAX - a; i++){ DP[i + a] = Math.min(DP[i + a], DP[i] + 1); }
					for(int i = 0; i <= MAX - b; i++){ DP[i + b] = Math.min(DP[i + b], DP[i] + 1); }
					for(int i = 0; i <= MAX - c; i++){ DP[i + c] = Math.min(DP[i + c], DP[i] + 1); }
					
					//System.out.println(Arrays.toString(DP));
					answer = Math.min(answer, DP[v0] + DP[v1] + DP[v2] + DP[v3]);
				}
			}
		}
		
		System.out.println(answer);
	}
}