#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int (i) = 0 ; (i) < (int)(n) ; (i)++)
#define REP(i,a,b) for(int (i) = a ; (int)(i) <= (int)(b) ; (i)++)
#define all(n) (n).begin(),(n).end()
typedef vector<int> Vi;
typedef vector<Vi> VVi;
typedef pair<int,int> Pii;
typedef vector<Pii> VPii;

int main(){
	int v[4];
	rep(i,4) cin >> v[i];
	int ans = 100000000;
	REP(i,1,30){
		REP(j,1,30){
			REP(k,1,30){
				int dp[64] = {};
				fill(dp,dp+64,100000000);
				dp[0] = 0;
				rep(l,32) dp[l+i] = min(dp[l+i],dp[l]+1);
				rep(l,32) dp[l+j] = min(dp[l+j],dp[l]+1);
				rep(l,32) dp[l+k] = min(dp[l+k],dp[l]+1);
				ans = min(ans,dp[v[0]]+dp[v[1]]+dp[v[2]]+dp[v[3]]);
			}
		}
	}
	cout << ans << endl;
	
}