#include <bits/stdc++.h>
using namespace std;
using ll = long long;
const int MOD = 998244353;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n, k;
  cin >> n >> k;
  vector<pair<int, int>> segments;
  ;
  for (int i = 0; i < k; ++i) {
    int l, r;
    cin >> l >> r;
    segments.push_back({l, r});
  }
  vector<ll> dp(n + 1, 0);
  dp[1] = 1;
  vector<ll> pref(n + 1, 0);
  pref[1] = 1;
  for (int i = 2; i <= n; ++i) {
    for (int j = 0; j < k; ++j) {
      int l = segments[j].first;
      int r = segments[j].second;
      dp[i] =
          (dp[i] + (pref[max(0, i - l)] - pref[max(0, i - r - 1)]) % MOD) % MOD;
    }
    pref[i] = (pref[i - 1] + dp[i]) % MOD;
  }
  cout << dp[n] << "\n";
}
