#include <bits/stdc++.h>
using namespace std;
const int mod = 998244353;
const int maxn = 200000 + 5;
int f[maxn], a[maxn], b[maxn];
int c[20];
int main() {
  int n, m;
  scanf("%d%d", &n, &m);
  for (int i = 0; i < m; ++i) scanf("%d%d", &a[i], &b[i]);
  f[1] = 1;
  for (int i = 2; i <= n; ++i)
    for (int j = 0; j < m; ++j) {
      c[j] += (i - a[j] >= 1 ? f[i - a[j]] : 0) -
              (i - b[j] - 1 >= 1 ? f[i - b[j] - 1] : 0);
      f[i] = (f[i] + c[j]) % mod;
    }
  cout << f[n];
  return 0;
}
