#include<bits/stdc++.h>
using namespace std;

typedef long long int ll;
typedef unsigned long long int llu;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef vector<pair<int, int> > vii;

#define rrep(i, m, n) for(i=m; i<n;  i++)
#define erep(i, n)    for(int i=1; i<=n; i++)
#define  rep(i, n)    for(i=0; i<n;  i++)
#define rrev(i, m, n) for(int i=n-1; i>=m; i--)
#define erev(i, n)    for(int i=n; i>=1; i--)
#define  rev(i, n)    for(int i=n-1; i>=0; i--)
#define EACH(v)       (v).begin(), (v).end()
#define CNT(a, n, x)  (upper_bound(a, a+n, x)-lower_bound(a, a+n, x))
#define minup(m, x)   (m=min(m, x))
#define maxup(m, x)   (m=max(m, x))
#define mp            make_pair

#define INF 100000000
#define MOD 1000000009
#define EPS 1E-9

#define drep(i, m, n, d) for(int i=m; i<=n; i+=d)
#define MAX_V 30

int i, j;
int v[4];
int res = INF;
int dp[MAX_V+1];
int d[3];

int main()
{

  rep(i, 4) cin >> v[i];
  rep(i, 4) v[i] -= 1;
  sort(v, v+4);

  rep(d[0], MAX_V) rep(d[1], MAX_V) rep(d[2], MAX_V){
    bool flag = true;
    int cnt = 0;
    rep(i, MAX_V) dp[i] = INF;
    rep(i, 3) dp[d[i]] = 1;
    rrep(i, d[0], MAX_V)  rep(j, 3) if(i - d[j] > 0) minup(dp[i], dp[i - d[j] - 1] + 1);
    rep(i, 4) cnt += dp[v[i]];
    minup(res, cnt);
  }

  cout << res << endl;

  return 0;
}