#include <bits/stdc++.h>
using namespace std;
const int mod = 998244353;
inline void add(int &a, int b) { (a += b) >= mod && (a -= mod); }
inline int mul(int a, int b) { return 1LL * a * b - 1LL * a * b / mod * mod; }
int n, m;
int c[1000005];
int a[1000005];
vector<int> cols;
vector<int> ind[505];
int dp[1005][1005];
int dfs(int l, int r) {
  if (l > r) return 1;
  if (~dp[l][r]) return dp[l][r];
  int &res = dp[l][r];
  res = 0;
  int mn = *min_element(a + l, a + r + 1);
  int lpos = ind[mn][0], rpos = ind[mn].back();
  if (l > lpos || r < rpos) return 0;
  int left = 0, right = 0;
  for (int i = l; i <= lpos; ++i)
    add(left, mul(dfs(l, i - 1), dfs(i, lpos - 1)));
  for (int i = rpos; i <= r; ++i)
    add(right, mul(dfs(rpos + 1, i), dfs(i + 1, r)));
  res = mul(left, right);
  for (int i = 0; i < (int)ind[mn].size() - 1; ++i)
    res = mul(res, dfs(ind[mn][i] + 1, ind[mn][i + 1] - 1));
  return res;
}
int main() {
  scanf("%d %d", &n, &m);
  for (int i = 1; i <= m; ++i) {
    scanf("%d", c + i);
    if (cols.empty() || cols.back() != c[i]) cols.push_back(c[i]);
  }
  m = (int)cols.size();
  if (m >= 2 * n) return puts("0") & 0;
  for (int i = 0; i < m; ++i) a[i + 1] = cols[i];
  for (int i = 1; i <= m; ++i) ind[a[i]].push_back(i);
  memset(dp, -1, sizeof(dp));
  printf("%d\n", dfs(1, m));
  return 0;
}
