import java.util.*;

public class Main {
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int[] v = new int[4];
    for(int i = 0; i < 4; i++) {
      v[i] = sc.nextInt();
    }
    int[][][][] dp = new int[31][31][31][31];
    for(int i = 1; i < 31; i++) {
      for(int j = 1; j < 31; j++) {
        for(int k = 1; k < 31; k++) {
          dp[i][j][k][0] = 0;
          for(int s = 1; s < 31; s++) {
            int m = Integer.MAX_VALUE;
            if(s - i >= 0 && dp[i][j][k][s - i] != -1) m = Math.min(m, 1 + dp[i][j][k][s - i]);
            if(s - j >= 0 && dp[i][j][k][s - j] != -1) m = Math.min(m, 1 + dp[i][j][k][s - j]);
            if(s - k >= 0 && dp[i][j][k][s - k] != -1) m = Math.min(m, 1 + dp[i][j][k][s - k]);
            if(m == Integer.MAX_VALUE) m = -1;
            dp[i][j][k][s] = m;
          }
        }
      }
    }
    int ans = Integer.MAX_VALUE;
    for(int i = 1; i < 31; i++) {
      for(int j = 1; j < 31; j++) {
        for(int k = 1; k < 31; k++) {
          int t = 0;
          for(int l = 0; l < 4; l++) {
            if(dp[i][j][k][v[l]] != -1) {
              t += dp[i][j][k][v[l]];
            } else {
              t = Integer.MAX_VALUE;
              break;
            }
          }
          ans = Math.min(ans, t);
        }
      }
    }
    System.out.println(ans);
  }
}