#include"bits/stdc++.h"

//#include<bits/stdc++.h>
using namespace std;
#define print(x) cout<<x<<endl;
#define rep(i,a,b) for(int i=a;i<b;i++)
#define REP(i,a) for(int i=0;i<a;i++)
typedef long long ll;
const ll mod = 10000000000;


int v[4];

int main() {
	cin >> v[0] >> v[1] >> v[2] >> v[3];
	int max = 31;
	int ans = 999;
	rep(i, 1, max)rep(j, i + 1, max)rep(k, j + 1, max) {
		vector<int> dp(max,999);
		dp[0] = 0;
		rep(l, 0, max-i) { dp[l + i] = min(dp[l + i], dp[l] + 1); }
		rep(l, 0, max-j) { dp[l + j] = min(dp[l + j], dp[l] + 1); }
		rep(l, 0, max-k) { 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]]);
	}
	print(ans);
	return 0;
}