#pragma GCC optimize("Ofast")
#define _USE_MATH_DEFINES
#include "bits/stdc++.h"

using namespace std;

using u8 = uint8_t;
using u16 = uint16_t;
using u32 = uint32_t;
using u64 = uint64_t;
using i8 = int8_t;
using i16 = int16_t;
using i32 = int32_t;
using i64 = int64_t;

constexpr char newl = '\n';
constexpr double eps = 1e-10;

#define FOR(i,a,b) for (int i = (a); i < (b); i++)
#define F0R(i,b) FOR(i,0,b)
#define RFO(i,a,b) for (int i = ((b)-1); i >=(a); i--)
#define RF0(i,b) RFO(i,0,b)
#define fi first
#define se second
#define debug(x) cout << #x << ": " << x << '\n';
#define rng(a) a.begin(),a.end()
#define rrng(a) a.rbegin(),a.rend()

template<typename T1, typename T2> inline void chmin(T1& a, T2 b) { if (a > b) a = b; }
template<typename T1, typename T2> inline void chmax(T1& a, T2 b) { if (a < b) a = b; }
template<class T> void Print(vector<T> v) {
  F0R(i, v.size()) {
    cout << v[i] << ' ';
  }
  cout << newl;
}
template<class T> bool lcmp(const pair<T, T>& l, const pair<T, T>& r) {
  return l.first < r.first;
}

#if 1

constexpr int MOD = 998244353;
template<int MOD>
struct Modint {
  long long val;
  constexpr Modint(long long v = 0) noexcept : val(v% MOD) {
    if (val < 0) val += MOD;
  }
  constexpr int getmod() { return MOD; }
  constexpr Modint operator - () const noexcept {
    return val ? MOD - val : 0;
  }
  constexpr Modint operator + (const Modint& r) const noexcept { return Modint(*this) += r; }
  constexpr Modint operator - (const Modint& r) const noexcept { return Modint(*this) -= r; }
  constexpr Modint operator * (const Modint& r) const noexcept { return Modint(*this) *= r; }
  constexpr Modint& operator += (const Modint& r) noexcept {
    val += r.val;
    if (val >= MOD) val -= MOD;
    return *this;
  }
  constexpr Modint& operator -= (const Modint& r) noexcept {
    val -= r.val;
    if (val < 0) val += MOD;
    return *this;
  }
  constexpr Modint& operator *= (const Modint& r) noexcept {
    val = val * r.val % MOD;
    return *this;
  }
  constexpr bool operator == (const Modint& r) const noexcept {
    return this->val == r.val;
  }
  constexpr bool operator != (const Modint& r) const noexcept {
    return this->val != r.val;
  }
  friend constexpr ostream& operator << (ostream& os, const Modint<MOD>& x) noexcept {
    return os << x.val;
  }
  friend constexpr istream& operator >> (istream& is, Modint<MOD>& x) noexcept {
    return is >> x.val;
  }

  constexpr Modint<MOD> pow(long long n) const noexcept {
    if (!n) return 1;
    auto t = pow(n >> 1);
    t *= t;
    if (n & 1) t *= *this;
    return t;
  }
  friend constexpr Modint<MOD> modpow(const Modint<MOD>& a, long long n) noexcept {
    return a.pow(n);
  }

  friend constexpr Modint<MOD> Ncr(Modint<MOD> a, int n) {
    Modint<MOD> p = 1, q = 1;

    while (n > 0) {
      p *= a;
      a -= 1;
      q *= n--;
    }

    return p / q;
  }

  // for prime mod
  constexpr Modint inv() const { return pow(MOD - 2); }
  constexpr Modint& operator /= (const Modint& r) noexcept {
    long long a = r.val, b = MOD, u = 1, v = 0;
    while (b) {
      long long t = a / b;
      a -= t * b; swap(a, b);
      u -= t * v; swap(u, v);
    }
    val = val * u % MOD;
    if (val < 0) val += MOD;
    return *this;
  }
  constexpr Modint operator / (const Modint& r) const noexcept { return Modint(*this) /= r; }
};
using mint = Modint<MOD>;


// INSERT ABOVE HERE
signed main() {
  cin.tie(0);
  ios_base::sync_with_stdio(false);

  int N, K;
  cin >> N >> K;
  vector<pair<int, int>> lr(K);
  F0R(i, K) {
    cin >> lr[i].first >> lr[i].second;
    lr[i].second++;
  }
  vector<mint> as(N), bs(K);
  as[0] = 1;
  F0R(i, N) {
    F0R(j, K) {
      if (i - lr[j].first >= 0) bs[j] += as[i - lr[j].first];
      if (i - lr[j].second >= 0) bs[j] -= as[i - lr[j].second];
      //debug(bs[j]);
      as[i] += bs[j];
      //debug((i - lr[j].first));
      //debug((i - lr[j].second));
    }
  }
  //Print(as);
  cout << as.back();
}
#endif


Measured memory_bytes: 4796