#include<iostream>
#include<cstring>
#include<vector>
#include<random>
#include<map>
using namespace std;
using LL = long long;
const int maxn = 3e5 + 5;
const int M = 1e9, N = 1e6 + 100;

mt19937_64 rnd(41432153252);
uniform_int_distribution<int> dist(M / 2, M);
const int mod1 = dist(rnd), mod2 = dist(rnd);
pair<int, int> pow2[N + 5], s[maxn];

int stk[maxn], a[maxn], ls[maxn], rs[maxn];

auto add(pair<int, int> a, pair<int, int> b){
    pair<int, int> c{a.first + b.first, a.second + b.second};
    if (c.first >= mod1) c.first -= mod1;
    if (c.second >= mod2) c.second -= mod2;
    return c;
};

auto sub(pair<int, int> a, pair<int, int> b){
    pair<int, int> c{a.first - b.first, a.second - b.second};
    if (c.first < 0) c.first += mod1;
    if (c.second < 0) c.second += mod2;
    return c;
};

int build(int n){
    int top = 0;
    for(int i = 1; i <= n; i++){
        int pos = top;
        while(pos && a[stk[pos]] < a[i]) pos--;
        if (pos) rs[stk[pos]] = i;
        if (pos < top) ls[i] = stk[pos + 1];
        stk[top = ++pos] = i;
    }
    return stk[1];
}

map<pair<int, int>, int> mp;
vector<int> pos[maxn];

void dfs(int u, int l, int r) {
    pos[u].push_back(u);
    if (l == r){
        return;
    }
    if (u - l <= r - u){
        for(int i = l; i <= u; i++){
            for(int j = 1; j <= 20; j++){
                auto target = add(pow2[a[u] + j], s[i - 1]);
                if (mp.contains(target)){
                    int R = mp[target];
                    if (R >= u and R <= r){
                        pos[R].push_back(i);
                    }
                }
            }
        }
    }
    else{
        for(int i = u; i <= r; i++){
            for(int j = 1; j <= 20; j++){
                auto target = sub(s[i], pow2[a[u] + j]);
                if (mp.contains(target)){
                    int L = mp[target] + 1;
                    if (L >= l and L <= u){
                        pos[i].push_back(L);
                    }
                }
            }
        }
    }
    if (ls[u]) dfs(ls[u], l, u - 1);
    if (rs[u]) dfs(rs[u], u + 1, r);
}

template<const int T>
struct ModInt {
    const static int mod = T;
    int x;
    ModInt(int x = 0) : x(x % mod) {}
    ModInt(long long x) : x(int(x % mod)) {} 
    int val() { return x; }
    ModInt operator + (const ModInt &a) const { int x0 = x + a.x; return ModInt(x0 < mod ? x0 : x0 - mod); }
    ModInt operator - (const ModInt &a) const { int x0 = x - a.x; return ModInt(x0 < 0 ? x0 + mod : x0); }
    ModInt operator * (const ModInt &a) const { return ModInt(1LL * x * a.x % mod); }
    ModInt operator / (const ModInt &a) const { return *this * a.inv(); }
    bool operator == (const ModInt &a) const { return x == a.x; };
    bool operator != (const ModInt &a) const { return x != a.x; };
    void operator += (const ModInt &a) { x += a.x; if (x >= mod) x -= mod; }
    void operator -= (const ModInt &a) { x -= a.x; if (x < 0) x += mod; }
    void operator *= (const ModInt &a) { x = 1LL * x * a.x % mod; }
    void operator /= (const ModInt &a) { *this = *this / a; }
    friend ModInt operator + (int y, const ModInt &a){ int x0 = y + a.x; return ModInt(x0 < mod ? x0 : x0 - mod); }
    friend ModInt operator - (int y, const ModInt &a){ int x0 = y - a.x; return ModInt(x0 < 0 ? x0 + mod : x0); }
    friend ModInt operator * (int y, const ModInt &a){ return ModInt(1LL * y * a.x % mod);}
    friend ModInt operator / (int y, const ModInt &a){ return ModInt(y) / a;}
    friend ostream &operator<<(ostream &os, const ModInt &a) { return os << a.x;}
    friend istream &operator>>(istream &is, ModInt &t){return is >> t.x;}

    ModInt pow(int64_t n) const {
        ModInt res(1), mul(x);
        while(n){
            if (n & 1) res *= mul;
            mul *= mul;
            n >>= 1;
        }
        return res;
    }
    
    ModInt inv() const {
        int a = x, b = mod, u = 1, v = 0;
        while (b) {
            int t = a / b;
            a -= t * b; swap(a, b);
            u -= t * v; swap(u, v);
        }
        if (u < 0) u += mod;
        return u;
    }
    
};
using mint = ModInt<1000000007>;

int main(){

#ifdef LOCAL
    freopen("data.in", "r", stdin);
    freopen("data.out", "w", stdout);
#endif

    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);

    pow2[0] = {1, 1};
    for(int i = 1; i <= N; i++){
        pow2[i] = add(pow2[i - 1], pow2[i - 1]);
    }

    int n;
    cin >> n;
    for(int i = 1; i <= n; i++){
        cin >> a[i];
        s[i] = add(s[i - 1], pow2[a[i]]);
    }
    for(int i = 0; i <= n; i++){
        mp[s[i]] = i;
    }
    dfs(build(n), 1, n);
    vector<mint> dp(n + 1);
    dp[0] = 1;
    for(int i = 1; i <= n; i++){
        for(auto l : pos[i]){
            dp[i] += dp[l - 1];
        }
    }
    cout << dp[n] << '\n';

}