#include <bits/stdc++.h>
using namespace std;
template <class T>
struct rge {
  T b, e;
};
template <class T>
rge<T> range(T i, T j) {
  return rge<T>{i, j};
}
struct debug {
  template <class T>
  debug& operator<<(const T&) {
    return *this;
  }
};
using ll = long long;
template <typename T>
void min_self(T& a, T b) {
  a = min(a, b);
}
template <typename T>
void max_self(T& a, T b) {
  a = max(a, b);
}
const int mod = 998244353;
inline int add(int a, int b) {
  a += b;
  while (a >= mod) a -= mod;
  while (a < 0) a += mod;
  return a;
}
inline void add_self(int& a, int b) { a = add(a, b); }
inline int mul(int a, int b) { return 1LL * a * b % mod; }
inline void mul_self(int& a, int b) { a = mul(a, b); }
inline int mpow(int a, int n) {
  int res = 1;
  while (n > 0) {
    if (n & 1) {
      res = mul(res, a);
    }
    a = mul(a, a);
    n >>= 1;
  }
  return res;
}
inline int divide(int a, int b) {
  assert(b != 0);
  return mul(a, mpow(b, mod - 2));
}
const int mxN = 200 * 1000 + 5;
int fact[mxN], finv[mxN];
inline int binomial(int n, int k) {
  return mul(fact[n], mul(finv[n - k], finv[k]));
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n, m;
  cin >> n >> m;
  vector<int> a(m);
  for (int i = 0; i < m; i++) {
    cin >> a[i];
    --a[i];
  }
  a.resize(unique(a.begin(), a.end()) - a.begin());
  m = a.size();
  if (m > 2 * n) {
    cout << "0\n";
    return 0;
  }
  vector<vector<int>> pos(n);
  for (int i = 0; i < m; i++) {
    pos[a[i]].push_back(i);
  }
  vector<vector<int>> dp(m + 1, vector<int>(m + 1, 1));
  for (int len = 1; len <= m; len++) {
    for (int i = 0; i <= m - len; i++) {
      int small = a[i];
      for (int j = 0; j < len; j++) {
        min_self(small, a[i + j]);
      }
      int L = pos[small][0] - i;
      int R = pos[small].back() - i;
      if (L < 0 || R >= len) {
        dp[i][len] = 0;
        continue;
      }
      int sum_on_left = 0, sum_on_right = 0;
      for (int j = 0; j <= L; j++) {
        add_self(sum_on_left, mul(dp[i][j], dp[i + j][L - j]));
      }
      for (int j = R + 1; j <= len; j++) {
        add_self(sum_on_right,
                 mul(dp[i + R + 1][j - (R + 1)], dp[i + j][len - j]));
      }
      dp[i][len] = mul(sum_on_left, sum_on_right);
      for (int j = 0; j < (int)pos[small].size() - 1; j++) {
        if (pos[small][j] + 1 != pos[small][j + 1]) {
          mul_self(
              dp[i][len],
              dp[pos[small][j] + 1][pos[small][j + 1] - pos[small][j] - 1]);
        }
      }
    }
  }
  cout << dp[0][m] << '\n';
}
