#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 100000001

int main(){
	
	vector<int> v(4);
	rep(i,4)cin>>v[i];
	int ans = Inf;
	for(int i=1;i<=30;i++){
		for(int j=i+1;j<=30;j++){
			for(int k=j+1;k<=30;k++){
				
				vector<int> dp(31,Inf);
				dp[0] = 0;
				rep(l,31){
					if(l+i<=30)dp[l+i] = min(dp[l+i],dp[l]+1);
					if(l+j<=30)dp[l+j] = min(dp[l+j],dp[l]+1);
					if(l+k<=30)dp[l+k] = min(dp[l+k],dp[l]+1);
				}
				
				int sum = 0;
				rep(l,4)sum += dp[v[l]];
				ans = min(ans,sum);
				
			}
		}
	}
	
	cout<<ans<<endl;
	
	return 0;
}