#include <bits/stdc++.h>

using namespace std;

const int N = 2010, MOD = 998244353;
inline int Plus(int a, int b) {return a + b >= MOD ? a + b - MOD : a + b; }
inline int Minus(int a, int b) {return a - b < 0 ? a - b + MOD : a - b; }
inline int ksm(long long a, int b) {
    long long r = 1;
    while(b) {
        if(b & 1) r = r * a % MOD;
        b >>= 1, a = a * a % MOD;
    }
    return r;
}
int n, A[N], inv[N];

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

    cin >> n;
    for(int i = 0; i <= n; i ++) cin >> A[i];
    inv[1] = 1;
    for(int i = 2; i < N; i ++)
        inv[i] = 1ll * (MOD - MOD / i) * inv[MOD % i] % MOD;
    
    int flag = 0;
    while(flag <= n && A[flag] >= flag) flag ++;

    // f[0] = 0
    int res = (flag > n);
    for(int k = 1; k <= n; k ++) {
        static int f[N];
        for(int i = n; i >= 0; i --) {
            f[i] = A[i];
            if(i + k <= n) f[i] = min(f[i], f[i + k]);
        }
        for(int i = n; i >= 0; i --) {
            if(f[i] < i) f[i] = 0;
            else if(i > n / 2) f[i] = 1;
            else f[i] = (min(n / 2, f[i]) - i) / k + 1;
        }
        f[0] = 1; int cnt_0 = 0, S = 1;
        for(int i = n; i >= 0; i --) {
            if(!f[i]) cnt_0 ++;
            else S = 1ll * S * f[i] % MOD;
            if(i + k <= n) {
                if(!f[i + k]) cnt_0 --;
                else S = 1ll * S * inv[f[i + k]] % MOD;
                if(i <= flag && !cnt_0) res = Plus(res, S);
            }
        }
    }

    // f[0] > 0, k | f[0]
    for(int k = 1; k <= n / 2; k ++) {
        int S = 1;
        for(int i = 0; i < k; i ++) {
            int minv = n / 2;
            for(int j = i; j <= n; j += k) minv = min(minv, A[j]);
            if(minv < i) {S = 0; break; }
            else S = 1ll * S * ((minv - i) / k + (i > 0)) % MOD;
        }
        res = Plus(res, S);
    }
    //f[0] > 0, k \not\mid f[0]
    for(int k = 2; (k - 1) <= n / 2; k += 2) {
        int S = 1;
        for(int i = 0; i < k; i ++) {
            int minv = n / 2;
            for(int j = i; j <= n; j += k) minv = min(minv, A[j]);
            int o = i;
            if(o < k / 2) o += k / 2;
            else o -= k / 2;
            if(minv < o) {S = 0; break; }
            S = 1ll * S * ((minv - o + k) / k) % MOD;
        }
        res = Plus(res, S);
    }

    cout << res << '\n';

    return 0;
}