#include <iostream>
#include <vector>
#include <algorithm>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
using ll = long long;
#define REP(i, n) for(ll i=0; i<(n);i++)
#define PER(i, n) for(ll i=n-1; i>=0;i--)

int main() {
  ll n, m;
  cin >> n >> m;
  vector<ll> cnt(n + 1);
  REP(i, m) {
    ll l, r;
    cin >> l >> r;
    cnt[r - l + 1]++;
  }
  if (n % 2) {
    cout << 0;
    return 0;
  }
  vector<mint> f(n + 1, 1), rf(n + 1, 1);
  REP(i, n) {
    f[i + 1] = f[i] * (i + 1);
    rf[i + 1] = mint(1) / f[i + 1];
  }


  vector<mint> p = { 1 };
  REP(d, n + 1) {    
    if (d % 2 || cnt[d] == 0)
      continue;
    mint vv = -f[d] * rf[d / 2] * rf[d / 2] / (d / 2 + 1);
    if (cnt[d] < 35) {
      p.resize(p.size() + d / 2 * cnt[d]);
      REP(i, cnt[d]) {
        PER(i, p.size() - d / 2) {
          p[i + d / 2] += vv * p[i];
        }
      }
    }
    else {
      vector<mint> mul(d / 2 * cnt[d] + 1);
      REP(i, cnt[d] + 1) {
        mul[d / 2 * i] = vv.pow(i) * f[cnt[d]] * rf[i] * rf[cnt[d] - i];
      }
      p = convolution(p, mul);
    }
  }
  mint ans = 0;
  REP(i, p.size()) {
    ans += p[i] * f[n - i * 2] * rf[n / 2 - i] * rf[n / 2 - i] / (n / 2 - i + 1);
  }
  cout << ans.val();

  return 0;
}