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

#define nl "\n"
#define ll long long
#define mod  1'000'000'007
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define sz(v) (int) v.size()

template<typename T = int>
istream &operator>>(istream &in, vector<T> &v) {
    for (auto &x: v) in >> x;
    return in;
}

template<typename T = int>
ostream &operator<<(ostream &out, const vector<T> &v) {
    for (const T &x: v) out << x << " ";
    return out;
}

void Sira() {
    ios_base::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#ifndef ONLINE_JUDGE
    freopen("input.txt", "r", stdin), freopen("output.txt", "w", stdout);
#endif
}
struct node {
    ll val;

    node(){
        val = -1e18;
    }

    node(ll v){
        val = v;
    }


};

struct SegTree{
    int seg_size = 1;
    vector < node > tree;

    SegTree(int n){
        while(seg_size < n) seg_size *= 2;
        tree.assign(2 * seg_size, node());
    }

    node merge(node a, node b){
        node res = node();
        res.val = max(a.val, b.val);
        return res;
    }

    void build(vector < int > &a, int x, int lx, int rx){
        if(rx - lx == 1){
            if(lx < sz(a)){
                tree[x] = node(a[lx]);
            }
            return;
        }
        int m = (lx + rx) / 2;
        build(a, 2 * x + 1, lx, m);
        build(a, 2 * x + 2, m, rx);
        tree[x] = merge(tree[2 * x + 1], tree[2 * x + 2]);
    }

    void build(vector < int > &a){
        build(a, 0, 0, seg_size);
    }

    void update(int idx , int val , int ni , int lx , int rx){
        if(rx - lx == 1){
            tree[ni] = node(val);
            return;
        }
        int m = (lx + rx) / 2;
        if(idx < m){
            update(idx, val, 2 * ni + 1, lx, m);
        }else{
            update(idx, val, 2 * ni + 2, m, rx);
        }
        tree[ni] = merge(tree[2 * ni + 1], tree[2 * ni + 2]);
    }

    void update(int idx, int val){
        update(idx, val, 0, 0, seg_size);
    }

    node query(int l, int r, int ni, int lx, int rx){
        if(lx >= r || l >= rx) return node();
        if(lx >= l && rx <= r) return tree[ni];
        int m = (lx + rx) / 2;
        node s1 = query(l, r, 2 * ni + 1, lx, m);
        node s2 = query(l, r, 2 * ni + 2, m, rx);
        return merge(s1, s2);
    }

    node query(int l, int r){
        return query(l, r, 0, 0, seg_size);
    }
};


void solve(){
    int n;
    cin >> n;
    vector < int > v(n);
    cin >> v;

    SegTree st(n);
    st.build(v);

    cout << st.query(0, 3).val << nl;

}

int main() {
    Sira();
    int t = 1;
//    cin >> t;
    while(t--){
        solve();
    }
    return 0;
}