#include <bits/stdc++.h>
using namespace std;
const int maxn = 1111, mod = 998244353;
inline long long read() {
  char ch = getchar();
  long long x = 0, f = 0;
  while (ch < '0' || ch > '9') f |= ch == '-', ch = getchar();
  while (ch >= '0' && ch <= '9') x = x * 10 + ch - '0', ch = getchar();
  return f ? -x : x;
}
int n, m, m_, a[maxn], lft[maxn], rig[maxn], f[maxn][maxn];
int main() {
  n = read();
  m_ = read();
  while (m_--) {
    int x = read();
    if (x != a[m]) a[++m] = x;
  }
  if (m > 2 * n) return puts("0"), 0;
  memset(lft, 0x3f, sizeof(lft));
  for (int i = (1); i <= (m); i++)
    lft[a[i]] = min(lft[a[i]], i), rig[a[i]] = max(rig[a[i]], i);
  for (int i = (1); i <= (m); i++)
    if (lft[a[i]] == i && rig[a[i]] == i) f[i][i] = 1;
  for (int i = (0); i <= (m); i++) f[i + 1][i] = f[i + 2][i] = 1;
  for (int l = (2); l <= (m); l++)
    for (int i = (1); i <= (m - l + 1); i++) {
      int j = i + l - 1, mn = i;
      for (int k = (i + 1); k <= (j); k++)
        if (a[k] < a[mn]) mn = k;
      int x = lft[a[mn]], y = rig[a[mn]], s1 = 0, s2 = 0, pre = 0;
      if (x < i || y > j) continue;
      for (int k = (i); k <= (x); k++)
        s1 = (s1 + 1ll * f[i][k - 1] * f[k][x - 1]) % mod;
      for (int k = (y); k <= (j); k++)
        s2 = (s2 + 1ll * f[y + 1][k] * f[k + 1][j]) % mod;
      f[i][j] = 1ll * s1 * s2 % mod;
      for (int k = (i); k <= (j); k++)
        if (a[k] == a[mn]) {
          if (pre) f[i][j] = 1ll * f[i][j] * f[pre + 1][k - 1] % mod;
          pre = k;
        }
    }
  printf("%d\n", f[1][m]);
}
