#include <bits/stdc++.h>

using namespace std;

#define FOR(i,a,b) for(int i=(a);i<(b);i++)
#define REP(i,n) FOR(i,0,n)
#define ALL(v) (v).begin(),(v).end()

template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }

typedef unsigned long long ull;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<int, pii> P;

const ll INF = 1ll<<29;
const ll MOD = 1000000007;
const double EPS  = 1e-10;

int main() {
	int v[4];
	REP(i, 4) scanf("%d", v + i);
	
	int ans = INF;
	
	FOR(i, 1, 31) FOR(j, i + 1, 31) FOR(k, j + 1, 31) {
		int dp[31];
		fill(dp, dp + 31, INF);
		
		dp[0] = 0;
		REP(l, 31) {
			if (dp[l] == INF) continue;
			
			if (i + l <= 30) chmin(dp[i + l], dp[l] + 1);
			if (j + l <= 30) chmin(dp[j + l], dp[l] + 1);
			if (k + l <= 30) chmin(dp[k + l], dp[l] + 1);
		}
		
		bool ng = false;
		int now = 0;
		
		REP(l, 4) {
			if (dp[v[l]] == INF) ng = true;
			now += dp[v[l]];
		}
		
		if (ng) continue;
		chmin(ans, now);
	}
	
	cout << ans << endl;
	
	return 0;
}