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

/**
 * yukicoder no.27
 * @author scache
 *
 */
public class PreparationBoard {
	public static void main(String[] args) {
		PreparationBoard p = new PreparationBoard();
	}

	public PreparationBoard() {
		Scanner sc = new Scanner(System.in);
		int[] v =new int[4];
		for(int i=0;i<v.length;i++)
			v[i] = sc.nextInt();
		solve(v);
	}

	public void solve(int[] v) {
		Arrays.sort(v);
		int m = 30;
		
		int[] dp = new int[m+1];
	
		int res = 10000000;
		for(int i=1;i<=m;i++){
			for(int j=i+1;j<=m;j++){
				for(int k=j+1;k<=m;k++){
					Arrays.fill(dp, 10000000);
					dp[0] = 0;
					calc(dp, i, m);
					calc(dp, j, m);
					calc(dp, k, m);
					
					int r = 0;
					for(int l=0;l<v.length;l++)
						r += dp[v[l]];
					
					res = Math.min(res, r);
				}
			}
		}
		
		System.out.println(res);
	}
	
	
	private void calc(int[] dp, int t, int m){
		for(int i=t;i<=m;i++){
			if(i-t<0 || dp[i-t]>=10000000)
				continue;
			dp[i] = Math.min(dp[i], dp[Math.max(i-t, 0)] + 1);
		}
		
	}

}