#include <bits/stdc++.h>

using namespace std;

template <std::uint_fast64_t Modulus> class modint {
    using u64 = std::uint_fast64_t;
    u64 a;

    public:

    template <class INT>
    constexpr modint(const INT x = 0) noexcept : a(x >= 0 ? x % Modulus : x % int_fast64_t(Modulus) + Modulus) {}
    constexpr modint(const u64 x = 0) noexcept : a(x % Modulus) {}
    constexpr u64 &value() noexcept { return a; }
    constexpr const u64 &value() const noexcept { return a; }
    constexpr modint operator+(const modint rhs) const noexcept {
        return modint(*this) += rhs;
    }
    constexpr modint operator-(const modint rhs) const noexcept {
        return modint(*this) -= rhs;
    }
    constexpr modint operator*(const modint rhs) const noexcept {
        return modint(*this) *= rhs;
    }
    constexpr modint operator/(const modint rhs) const noexcept {
        return modint(*this) /= rhs;
    }
    constexpr modint &operator+=(const modint rhs) noexcept {
        a += rhs.a;
        if (a >= Modulus) {
            a -= Modulus;
        }
        return *this;
    }
    constexpr modint &operator-=(const modint rhs) noexcept {
        if (a < rhs.a) {
            a += Modulus;
        }
        a -= rhs.a;
        return *this;
    }
    constexpr modint &operator*=(const modint rhs) noexcept {
        a = a * rhs.a % Modulus;
        return *this;
    }
    constexpr modint &operator/=(modint rhs) noexcept {
        u64 exp = Modulus - 2;
        while (exp) {
            if (exp % 2) {
                *this *= rhs;
            }
        rhs *= rhs;
        exp /= 2;
        }
        return *this;
    }

    constexpr bool operator<(const modint& rhs) const noexcept {return this->a < rhs.a;}
    constexpr bool operator>(const modint& rhs) const noexcept {return rhs < *this;}
    constexpr bool operator<=(const modint& rhs) const noexcept {return !(*this > rhs);}
    constexpr bool operator>=(const modint& rhs) const noexcept {return !(*this < rhs);}
    constexpr bool operator==(const modint& rhs) const noexcept {return this->a == rhs.a;}
    constexpr bool operator!=(const modint& rhs) const noexcept {return !(*this == rhs);}

    constexpr modint& operator++() noexcept {
        *this += modint(1);
        return *this;
    }
    constexpr modint operator++(int) noexcept {
        modint tmp(*this);
        ++(*this);
        return tmp;
    }
    constexpr modint& operator--() noexcept {
        *this -= modint(1);
        return *this;
    }
    constexpr modint operator--(int) noexcept {
        modint tmp(*this);
        --(*this);
        return tmp;
    }
    constexpr modint operator-() const noexcept {
        return modint(0) - *this;
    }

    template <std::uint_fast64_t M>
    friend constexpr std::ostream& operator<<(std::ostream& os, const modint<M>& rhs) noexcept {
        os << rhs.a;
        return os;
    }
    template <std::uint_fast64_t M>
    friend constexpr std::istream& operator>>(std::istream& is, modint<M>& rhs) noexcept {
        int64_t tmp;
        is >> tmp;
        rhs = modint(tmp);
        return is;
    }

    constexpr modint pow(const u64 k) const noexcept {
        if (k == 0)
            return 1;
        if (k % 2 == 0){
            modint res = pow(k / 2);
            return res * res;
        }
        return pow(k - 1) * modint(*this);
    }

    template <typename T>
    operator const T (){return a;}
};


template< typename Monoid, typename OperatorMonoid = Monoid >
struct LazySegmentTree
{
  using F = function< Monoid(Monoid, Monoid) >;
  using G = function< Monoid(Monoid, OperatorMonoid) >;
  using H = function< OperatorMonoid(OperatorMonoid, OperatorMonoid) >;
  using P = function< OperatorMonoid(OperatorMonoid, int) >;

  int sz;
  vector< Monoid > data;
  vector< OperatorMonoid > lazy;
  const F f;
  const G g;
  const H h;
  const P p;
  const Monoid M1;
  const OperatorMonoid OM0;


  LazySegmentTree(int n, const F f, const G g, const H h, const P p,
                  const Monoid &M1, const OperatorMonoid OM0)
      : f(f), g(g), h(h), p(p), M1(M1), OM0(OM0)
  {
    sz = 1;
    while(sz < n) sz <<= 1;
    data.assign(2 * sz, M1);
    lazy.assign(2 * sz, OM0);
  }

  void set(int k, const Monoid &x)
  {
    data[k + sz] = x;
  }

  void build()
  {
    for(int k = sz - 1; k > 0; k--) {
      data[k] = f(data[2 * k + 0], data[2 * k + 1]);
    }
  }

  void propagate(int k, int len)
  {
    if(lazy[k] != OM0) {
      if(k < sz) {
        lazy[2 * k + 0] = h(lazy[2 * k + 0], lazy[k]);
        lazy[2 * k + 1] = h(lazy[2 * k + 1], lazy[k]);
      }
      data[k] = g(data[k], p(lazy[k], len));
      lazy[k] = OM0;
    }
  }

  Monoid update(int a, int b, const OperatorMonoid &x, int k, int l, int r)
  {
    propagate(k, r - l);
    if(r <= a || b <= l) {
      return data[k];
    } else if(a <= l && r <= b) {
      lazy[k] = h(lazy[k], x);
      propagate(k, r - l);
      return data[k];
    } else {
      return data[k] = f(update(a, b, x, 2 * k + 0, l, (l + r) >> 1),
                         update(a, b, x, 2 * k + 1, (l + r) >> 1, r));
    }
  }

  Monoid update(int a, int b, const OperatorMonoid &x)
  {
    return update(a, b, x, 1, 0, sz);
  }


  Monoid query(int a, int b, int k, int l, int r)
  {
    propagate(k, r - l);
    if(r <= a || b <= l) {
      return M1;
    } else if(a <= l && r <= b) {
      return data[k];
    } else {
      return f(query(a, b, 2 * k + 0, l, (l + r) >> 1),
               query(a, b, 2 * k + 1, (l + r) >> 1, r));
    }
  }

  Monoid query(int a, int b)
  {
    return query(a, b, 1, 0, sz);
  }

  Monoid operator[](const int &k)
  {
    return query(k, k + 1);
  }
};


const constexpr int64_t p = 998244353;
using mint = modint<p>;

int main(){
    
    int n, k;
    cin >> n >> k;

    auto f = [](mint a, mint b) { return a + b; };
    auto p = [](mint a, mint b) { return a * b; };
    LazySegmentTree<mint, mint> DP(n + 1, f, f, f, p, mint(0), mint(0));
    DP.update(1, 2, mint(1));
    vector<int> L(k), R(k);

    for (int i = 0; i < k; i++){
        int l, r;
        cin >> L[i] >> R[i];
    }
    for (int j = 1; j <= n; j++){
        for (int i = 0; i < k; i++){
            const auto l = L[i], r = R[i];
            DP.update(min(n + 1, j + l), min(n + 1, j + r + 1), DP.query(j, j + 1));
        }
    }

    cout << DP.query(n, n + 1) << endl;
}

Measured memory_bytes: 11476