#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define elif else if
#define sp(x) fixed << setprecision(x)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
using ll = long long;
using ld = long double;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
const ll MOD = 1e9+7;
//const ll MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
const ld EPS = 1e-10;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};

int main(){
    ll A[5];
    rep(i, 5) cin >> A[i];
    ll l = 0, r = INF; //[l, r)
    while(r-l > 1){
        ll m = (l+r)/2;
        ll num[5];
        rep(i, 5){
            if(A[i]-m > 0) num[i] = 0;
            else num[i] = m-A[i];
        }
        ll M = 0;
        rep(i, 5) M += num[i];
        M = (M+1)/2;
        rep(i, 5){
            int j = (i+2)%5;
            chmax(M, num[i]+num[j]);
        }
        if(M <= m) l = m;
        else r = m;
    }
    cout << l << endl;
}