#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 each(e, v) for(auto &e: v)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
#define pq(type, name) priority_queue<type> name
#define iq(type, name) priority_queue<type, vector<type>, greater<type>> name
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
const double pi = acos(-1.0);
const double EPS = 1e-10;
template<typename T> bool chmax(T &x, const T &y){
    if(x < y) {x = y; return true;}
    return false;
}
template<typename T> bool chmin(T &x, const T &y){
    if(x > y) {x = y; return true;}
    return false;
}
void in() {}
template<typename Head, typename ...Tail> void in(Head &&head, Tail &&...tail){
    cin >> head;
    in(forward<Tail>(tail)...);
}
void out() {cout << '\n';}
template<typename Head, typename ...Tail> void out(Head &&head, Tail &&...tail){
    cout << head << ' ';
    out(forward<Tail>(tail)...);
}
void outn() {}
template<typename Head, typename ...Tail> void outn(Head &&head, Tail &&...tail){
    cout << head << '\n';
    outn(forward<Tail>(tail)...);
}
template<typename T, typename U> void in(pair<T, U> &p){
    cin >> p.first >> p.second;
}
template<typename T, typename U> void out(pair<T, U> p){
    cout << p.first << ' ' << p.second << '\n';
}
using vi = vector<int>;
using vll = vector<ll>;
#define vec1(type, name, ...) vector<type> name(__VA_ARGS__)
#define VEC1(type, ...) vector<type>(__VA_ARGS__)
#define vec2(type, name, a, ...) vector<vector<type>> name(a, VEC1(type, __VA_ARGS__))
#define VEC2(type, a, ...) vector<vector<type>>(a, VEC1(type, __VA_ARGS__))
#define vec3(type, name, a, b, ...) vector<vector<vector<type>>> name(a, VEC2(type, b, __VA_ARGS__))
#define VEC3(type, a, b, ...) vector<vector<vector<type>>>(a, VEC2(type, b, __VA_ARGS__))
#define vec4(type, name, a, b, c, ...) vector<vector<vector<vector<type>>>> name(a, VEC3(type, b, c, __VA_ARGS__))
#define VEC4(type, a, b, c, ...) vector<vector<vector<vector<type>>>>(a, VEC3(type, b, c, __VA_ARGS__))
#define vec5(type, name, a, b, c, d, ...) vector<vector<vector<vector<vector<type>>>>> name(a, VEC4(type, b, c, d, __VA_ARGS__))
#define VEC5(type, a, b, c, d, ...) vector<vector<vector<vector<vector<type>>>>>(a, VEC4(type, b, c, d, __VA_ARGS__))
template<typename T> void vin(vector<T> &a){
    rep(i, sz(a)) cin >> a[i];
}
template<typename T> void vout(const vector<T> &a){
    for(auto &e: a) cout << e << ' ';
    cout << '\n';
}
template<typename T> void voutn(const vector<T> &a){
    for(auto &e: a) cout << e << '\n';
}
template<typename T> void unique(vector<T> &a){
    sort(all(a)), a.erase(unique(all(a)), a.end());
}
vector<int> iota(int n){
    vector<int> ret(n);
    iota(all(ret), 0);
    return ret;
}
template<typename T> vector<int> iota(const vector<T> &a, bool greater = false){
    vector<int> ret = iota(sz(a));
    sort(all(ret), [&](int i, int j){
        return (a[i] < a[j])^greater;
    });
    return ret;
}
struct io_setup{
    io_setup(){
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        cout << fixed << setprecision(15);
    }
} io_setup;
#define VEC(type, name, n) vector<type> name(n); vin(name)
#define INT(...) int __VA_ARGS__; in(__VA_ARGS__)
#define LL(...) ll __VA_ARGS__; in(__VA_ARGS__)
#define CHAR(...) char __VA_ARGS__; in(__VA_ARGS__)
#define STR(...) string __VA_ARGS__; in(__VA_ARGS__)
#define DBL(...) double __VA_ARGS__; in(__VA_ARGS__)
//const int MOD = 1000000007;
const int MOD = 998244353;

template<int mod>
struct Mod_Int{
    ll x;

    Mod_Int() : x(0) {}

    Mod_Int(ll y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}

    Mod_Int &operator += (const Mod_Int &p){
        x = (x + p.x) % mod;
        return *this;
    }

    Mod_Int &operator -= (const Mod_Int &p){
        x = (x + mod - p.x) % mod;
        return *this;
    }

    Mod_Int &operator *= (const Mod_Int &p){
        x = (x * p.x) % mod;
        return *this;
    }

    Mod_Int &operator /= (const Mod_Int &p){
        *this *= p.inverse();
        return *this;
    }

    Mod_Int &operator ++ () {return *this += Mod_Int(1);}

    Mod_Int operator ++ (int){
        Mod_Int tmp = *this;
        ++*this;
        return tmp;
    }

    Mod_Int &operator -- () {return *this -= Mod_Int(1);}

    Mod_Int operator -- (int){
        Mod_Int tmp = *this;
        --*this;
        return tmp;
    }

    Mod_Int operator - () const {return Mod_Int(-x);}

    Mod_Int operator + (const Mod_Int &p) const {return Mod_Int(*this) += p;}

    Mod_Int operator - (const Mod_Int &p) const {return Mod_Int(*this) -= p;}

    Mod_Int operator * (const Mod_Int &p) const {return Mod_Int(*this) *= p;}

    Mod_Int operator / (const Mod_Int &p) const {return Mod_Int(*this) /= p;}

    bool operator == (const Mod_Int &p) const {return x == p.x;}

    bool operator != (const Mod_Int &p) const {return x != p.x;}

    Mod_Int inverse() const {
        assert(*this != Mod_Int(0));
        return pow(mod-2);
    }

    Mod_Int pow(ll k) const{
        Mod_Int now = *this, ret = 1;
        while(k){
            if(k&1) ret *= now;
            now *= now, k >>= 1;
        }
        return ret;
    }

    friend ostream &operator << (ostream &os, const Mod_Int &p){
        return os << p.x;
    }

    friend istream &operator >> (istream &is, Mod_Int &p){
        ll a;
        is >> a;
        p = Mod_Int<mod>(a);
        return is;
    }
};

using mint = Mod_Int<MOD>;

template<typename T>
struct Binary_Indexed_Tree{
    vector<T> bit;
    const int n;
    
    Binary_Indexed_Tree(const vector<T> &v) : n(sz(v)){
        bit.resize(n+1);
        copy(all(v), bit.begin()+1);
        for(int a = 2; a <= n; a <<= 1){
            for(int b = a; b <= n; b += a){
                bit[b] += bit[b-a/2];
            }
        }
    }
    
    void add(int i, const T &x){
        for(i++; i <= n; i += (i & -i)) bit[i] += x;
    }

    void change(int i, const T&x){
        add(i, x-query(i, i+1));
    }
    
    T sum(int i) const{
        T ret = 0;
        for(; i > 0; i -= (i & -i)) ret += bit[i];
        return ret;
    }
    
    T query(int l, int r) const{
        return sum(r) - sum(l);
    }

    int lower_bound(T x) const{
        int ret = 0;
        for(int k = 31-__builtin_clz(n); k >= 0; k--){
            if(ret+(1<<k) <= n && bit[ret+(1<<k)] < x) x -= bit[ret += (1<<k)]; 
        }
        return ret;
    }

    int upper_bound(T x) const {return lower_bound(x+1);}
};

int main(){
    INT(N);
    VEC(int, a, N);
    each(e, a) e--;
    vi id(5000, N);
    reverse(all(a));
    rep(i, N) id[a[i]] = i;
    rep2(i, 1, 4999){
        chmin(id[i], id[i-1]);
    }
    //rep(i, 10) cout << id[i]; cout << endl;
    vec2(mint, dp, N, 2500, 0);
    vec2(mint, sum, N, 2501, 0);
    int M = 0;
    rep(i, N-1) chmax(M, a[i]-a[i+1]);
    dp[0][M] = 1;
    rep(i, 2499) sum[0][i+1] = sum[0][i]+dp[0][i];
    vector<Binary_Indexed_Tree<mint>> bit;
    rep(i, 2500){
        bit.eb(vector<mint>(N, 0));
    }
    rep2(i, 2, N-1){
        rep3(k, 2499, M){
            int pre = id[a[i]+k];
            if(pre <= i-2 && a[pre] == a[i]+k){
                dp[i-1][k] += sum[pre][k];
            }
            dp[i-1][k] += bit[k].query(pre, i-1);
            bit[k].add(i-1, dp[i-1][k]);
        }
        rep(j, 2499) sum[i-1][j+1] = sum[i-1][j]+dp[i-1][j];
    }
    mint ans = 0;
    rep(i, N){
        rep(j, 2500){
            ans += dp[i][j]*j;
        }
    }
    out(ans*2);
}