//#define _GLIBCXX_DEBUG

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

#define endl '\n'
#define lfs cout<<fixed<<setprecision(10)
#define ALL(a)  (a).begin(),(a).end()
#define ALLR(a)  (a).rbegin(),(a).rend()
#define spa << " " <<
#define fi first
#define se second
#define MP make_pair
#define MT make_tuple
#define PB push_back
#define EB emplace_back
#define rep(i,n,m) for(ll i = (n); i < (ll)(m); i++)
#define rrep(i,n,m) for(ll i = (ll)(m) - 1; i >= (ll)(n); i--)
using ll = long long;
using ld = long double;
const ll MOD1 = 1e9+7;
const ll MOD9 = 998244353;
const ll INF = 1e18;
using P = pair<ll, ll>;
template<typename T1, typename T2>
bool chmin(T1 &a,T2 b){if(a>b){a=b;return true;}else return false;}
template<typename T1, typename T2>
bool chmax(T1 &a,T2 b){if(a<b){a=b;return true;}else return false;}
ll median(ll a,ll b, ll c){return a+b+c-max({a,b,c})-min({a,b,c});}
void ans1(bool x){if(x) cout<<"Yes"<<endl;else cout<<"No"<<endl;}
void ans2(bool x){if(x) cout<<"YES"<<endl;else cout<<"NO"<<endl;}
void ans3(bool x){if(x) cout<<"Yay!"<<endl;else cout<<":("<<endl;}
template<typename T1,typename T2>
void ans(bool x,T1 y,T2 z){if(x)cout<<y<<endl;else cout<<z<<endl;}  
template<typename T>
void debug(vector<vector<T>>&v,ll h,ll w){for(ll i=0;i<h;i++)
{cout<<v[i][0];for(ll j=1;j<w;j++)cout spa v[i][j];cout<<endl;}};
void debug(vector<string>&v,ll h,ll w){for(ll i=0;i<h;i++)
{for(ll j=0;j<w;j++)cout<<v[i][j];cout<<endl;}};
template<typename T>
void debug(vector<T>&v,ll n){if(n!=0)cout<<v[0];
for(ll i=1;i<n;i++)cout spa v[i];cout<<endl;};
template<typename T>
vector<vector<T>>vec(ll x, ll y, T w){
  vector<vector<T>>v(x,vector<T>(y,w));return v;}
ll gcd(ll x,ll y){ll r;while(y!=0&&(r=x%y)!=0){x=y;y=r;}return y==0?x:y;}
vector<ll>dx={1,-1,0,0,1,1,-1,-1};
vector<ll>dy={0,0,1,-1,1,-1,1,-1};
template<typename T>
vector<T> make_v(size_t a,T b){return vector<T>(a,b);}
template<typename... Ts>
auto make_v(size_t a,Ts... ts){
  return vector<decltype(make_v(ts...))>(a,make_v(ts...));
}
template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2>&p){
  return os << p.first << " " << p.second;
}
//mt19937 mt(chrono::steady_clock::now().time_since_epoch().count());
template< typename flow_t >
struct Dinic {
  const flow_t INF;

  struct edge {
    ll to;
    flow_t cap;
    ll rev;
    bool isrev;
  };

  vector< vector< edge > > graph;
  vector< ll > min_cost, iter;

  Dinic(ll V) : INF(numeric_limits< flow_t >::max()), graph(V) {}

  void add_edge(ll from, ll to, flow_t cap) {
    graph[from].emplace_back((edge) {to, cap, (ll) graph[to].size(), false});
    graph[to].emplace_back((edge) {from, 0, (ll) graph[from].size() - 1, true});
  }

  bool bfs(ll s, ll t) {
    min_cost.assign(graph.size(), -1);
    queue< ll > que;
    min_cost[s] = 0;
    que.push(s);
    while(!que.empty() && min_cost[t] == -1) {
      ll p = que.front();
      que.pop();
      for(auto &e : graph[p]) {
        if(e.cap > 0 && min_cost[e.to] == -1) {
          min_cost[e.to] = min_cost[p] + 1;
          que.push(e.to);
        }
      }
    }
    return min_cost[t] != -1;
  }

  flow_t dfs(ll idx, const ll t, flow_t flow) {
    if(idx == t) return flow;
    for(ll &i = iter[idx]; i < graph[idx].size(); i++) {
      edge &e = graph[idx][i];
      if(e.cap > 0 && min_cost[idx] < min_cost[e.to]) {
        flow_t d = dfs(e.to, t, min(flow, e.cap));
        if(d > 0) {
          e.cap -= d;
          graph[e.to][e.rev].cap += d;
          return d;
        }
      }
    }
    return 0;
  }

  flow_t max_flow(ll s, ll t) {
    flow_t flow = 0;
    while(bfs(s, t)) {
      iter.assign(graph.size(), 0);
      flow_t f = 0;
      while((f = dfs(s, t, INF)) > 0) flow += f;
    }
    return flow;
  }

  void output() {
    for(ll i = 0; i < graph.size(); i++) {
      for(auto &e : graph[i]) {
        if(e.isrev) continue;
        auto &rev_e = graph[e.to][e.rev];
        cout << i << "->" << e.to << " (flow: " << rev_e.cap << "/" << e.cap + rev_e.cap << ")" << endl;
      }
    }
  }
};
int main(){
  cin.tie(nullptr);
  ios_base::sync_with_stdio(false);
  ll res=0,buf=0;
  bool judge = true;
  vector<ll>a(5);
  rep(i,0,5)cin>>a[i];
  ll ok=0,ng=INF;
  while(ng-ok>=2){
    ll mid=(ok+ng)/2;
    Dinic<ll>dinic(12);
    rep(i,0,5){
      ll from=i;
      vector<ll>to(2);
      to[0]=(i+4)%5+5;
      to[1]=(i+1)%5+5;
      rep(j,0,2)dinic.add_edge(from,to[j],INF);
      dinic.add_edge(10,i,-min(0LL,a[i]-mid));
      dinic.add_edge(i+5,11,-min(0LL,a[i]-mid));
    }
    ll mx=dinic.max_flow(10,11);
    ll sum=0;
    rep(i,0,5)sum-=min(0LL,a[i]-mid);
    if(sum-mx+mx/2<=mid)ok=mid;
    else ng=mid;
  }
  cout<<ok<<endl;
  return 0;
}