#include <bits/stdc++.h>
template <unsigned MOD = 1000000007>
struct mint
{
    unsigned v;
    mint(unsigned v_ = 0) : v(v_) {}
    mint &operator+=(const mint &X) { return (v += X.v) >= MOD ? v -= MOD : v, *this; }
    mint &operator-=(const mint &X) { return (v += MOD - X.v) >= MOD ? v -= MOD : v, *this; }
    mint &operator*=(const mint &X) { return v = 1llu * v * X.v % MOD, *this; }
    mint &operator/=(const mint &X) { return *this *= X.inv(); }
    mint pow(long long B) const
    {
        mint res = 1, A = *this;
        while (B)
        {
            if (B & 1)
                res *= A;
            A *= A;
            B >>= 1;
        }
        return res;
    }
    friend mint operator+(const mint &A, const mint &B) { return mint(A) += B; }
    friend mint operator-(const mint &A, const mint &B) { return mint(A) -= B; }
    friend mint operator*(const mint &A, const mint &B) { return mint(A) *= B; }
    friend mint operator/(const mint &A, const mint &B) { return mint(A) /= B; }
    friend bool operator<(const mint &A, const mint &B) { return A.v < B.v; }
    friend bool operator==(const mint &A, const mint &B) { return A.v == B.v; }
    friend std::ostream &operator<<(std::ostream &A, const mint &B) { return A << B.v; }
};
mint<> dp[300005];
mint<998244853> pw[1000105];
int n, a[300005];
void solve(int l, int r)
{
    static int b[1000100], tag[1000100], tim;
    if (r - l == 1)
    {
        dp[r] += dp[l];
        return;
    }
    int mid = (l + r) >> 1;
    solve(l, mid);
    std::map<mint<998244853>, mint<>> map;
    mint<998244853> cur;
    map.clear();
    ++tim;
    cur = 0;
    for (int i = mid; i-- != l;)
        map[cur += pw[a[i]]] += dp[i];
    cur = 0;
    for (int i = mid, max = 0; i != r; ++i)
    {
        if (tag[a[i]] != tim)
            tag[a[i]] = tim, b[a[i]] = 0;
        ++b[a[i]];
        cur += pw[a[i]];
        max = std::max(max, a[i]);
        for (int j = a[i]; b[j] >= 2; ++j)
        {
            if (tag[j + 1] != tim)
                tag[j + 1] = tim, b[j + 1] = 0;
            b[j + 1] += b[j] >> 1;
            b[j] &= 1;
            max = std::max(max, j + 1);
        }
        dp[i + 1] += map[pw[max + 1] - cur];
    }
    map.clear();
    ++tim;
    cur = 0;
    for (int i = mid, max = 0; i-- != l;)
    {
        if (tag[a[i]] != tim)
            tag[a[i]] = tim, b[a[i]] = 0;
        ++b[a[i]];
        cur += pw[a[i]];
        max = std::max(max, a[i]);
        for (int j = a[i]; b[j] >= 2; ++j)
        {
            if (tag[j + 1] != tim)
                tag[j + 1] = tim, b[j + 1] = 0;
            b[j + 1] += b[j] >> 1;
            b[j] &= 1;
            max = std::max(max, j + 1);
        }
        if (cur == pw[max])
            continue;
        map[pw[max + 1] - cur] += dp[i];
    }
    cur = 0;
    for (int i = mid; i != r; ++i)
        dp[i + 1] += map[cur += pw[a[i]]];
    solve(mid, r);
}
signed main()
{
    std::ios::sync_with_stdio(false);
    pw[0] = 1;
    for (int i = 1; i <= 1000000; ++i)
        pw[i] = pw[i - 1] + pw[i - 1];
    std::cin >> n;
    for (int i = 0; i != n; ++i)
        std::cin >> a[i];
    dp[0] = 1;
    solve(0, n);
    std::cout << dp[n] << std::endl;
    return 0;
}