#include <bits/stdc++.h>   using namespace std;   template <typename T>   inline void read(T &x) {     x = 0;     bool f = false;     char ch = getchar();     while (!isdigit(ch)) {       f |= ch ==  - , ch = getchar();     }     while (isdigit(ch)) {       x = (x << 1) + (x << 3) + (ch ^ 48);       ch = getchar();     }     x = f ? -x : x;     return;   }   template <typename T>   inline void write(T x) {     if (x < 0) x = -x, putchar( - );     if (x > 9) write(x / 10);     putchar(x % 10 ^ 48);     return;   }   const int N = 1e3 + 5, MOD = 998244353;   int n, m, val[N], dp[N], Ans, C[N][N];   int main() {     read(n);     for (int i = 1; i <= n; i++) read(val[i]), C[i][i] = C[i][0] = 1;     for (int i = 1; i <= n; i++)       for (int j = 1; j < i; j++)         C[i][j] = (C[i - 1][j - 1] + C[i - 1][j] > +MOD                        ? C[i - 1][j - 1] + C[i - 1][j] - MOD                        : C[i - 1][j - 1] + C[i - 1][j]);     dp[n + 1] = 1;     for (int i = n; i >= 1; i--) {       if (val[i] <= 0) continue;       for (int j = val[i] + i + 1; j <= n + 1; j++)         dp[i] = (dp[i] + 1ll * dp[j] * C[j - i - 1][val[i]] % MOD > +MOD                      ? dp[i] + 1ll * dp[j] * C[j - i - 1][val[i]] % MOD - MOD                      : dp[i] + 1ll * dp[j] * C[j - i - 1][val[i]] % MOD);     }     for (int i = 1; i <= n; i++)       Ans = (Ans + dp[i] > +MOD ? Ans + dp[i] - MOD : Ans + dp[i]);     write(Ans);     return 0;   }   