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

#define TRACE(x) x
#define WATCH(x) TRACE(cout << #x" = " << x << endl)
#define WATCHR(a, b) TRACE(for (auto it=a; it!=b;) cout << *(it++) << " "; cout << endl)
#define WATCHC(V) TRACE({cout << #V" = "; WATCHR(V.begin(), V.end());})

#define all(x) (x).begin(), (x).end()

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vb = vector<bool>;
using vs = vector<string>;

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

template<int MOD> struct modnum {
    int v;
    modnum() : v(0) {}
    modnum(ll _v) : v(_v % MOD) { if (v < 0) v += MOD; }
    explicit operator int() const { return v; }
    friend ostream& operator << (ostream& o, const modnum& n) { return o << n.v; }
    friend istream& operator << (istream& i, modnum& n) { ll v; i >> v; n = modnum(v); return i; }

    friend bool operator == (const modnum& a, const modnum& b) { return a.v == b.v; }
    friend bool operator != (const modnum& a, const modnum& b) { return a.v != b.v; }

    modnum& operator += (const modnum& o) { v += o.v; if (v >= MOD) v -= MOD; return *this; }
    modnum& operator -= (const modnum& o) { v -= o.v; if (v < 0) v += MOD; return *this; }
    modnum& operator *= (const modnum& o) { v = int(ll(v) * ll(o.v) % MOD); return *this; }
    modnum operator - () { modnum res; if (v) res.v = MOD - v; return res; }
    friend modnum operator + (const modnum& a, const modnum& b) { return modnum(a) += b; }
    friend modnum operator - (const modnum& a, const modnum& b) { return modnum(a) -= b; }
    friend modnum operator * (const modnum& a, const modnum& b) { return modnum(a) *= b; }

    modnum pow(int e) const {
        if (e == 0) return 1;
        if (e & 1) return *this * this->pow(e-1);
        return (*this * *this).pow(e/2);
    }

    modnum inv() const {
        int g = MOD, x = 0, y = 1;
        for (int r = v; r != 0; ) {
            int q = g / r;
            g %= r; swap(g, r);
            x -= q * y; swap(x, y);
        }

        assert(g == 1);
        assert(y == MOD || y == -MOD);
        return x < 0 ? x + MOD : x;
    }
    modnum& operator /= (const modnum& o) { return (*this) *= o.inv(); }
    friend modnum operator / (const modnum& a, const modnum& b) { return modnum(a) /= modnum(b); }
};
using mn = modnum<1'000'000'007>;

pair<mn, mn> ways(const vi &h) {
    int mv = INT_MAX;
    for (int v : h) {
        mv = min(mv, v);
    }

    mn vert = 1, horiz = 1;

    auto proc = [&](vi &grp) {
        if (!grp.size()) return;
        auto p = ways(grp);
        grp.clear();

        horiz *= p.second;
        vert *= (p.first + p.second);
    };

    vi grp;
    for (int v : h) {
        if (v == mv) {
            vert *= 2;
            proc(grp);
        } else {
            grp.push_back(v - mv);
        }
    }
    proc(grp);

    mn checker = 2 * horiz;
    horiz *= mn(2).pow(mv);
    mn total = vert + horiz - checker;

    return { total, horiz };
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(0), cout.tie(0);

    int N;
    cin >> N;

    vi h(N);
    for (int i = 0; i < N; i++) {
        cin >> h[i];
    }

    cout << ways(h).first << endl;

    return 0;
}



Measured memory_bytes: 384