#include <bits/stdc++.h>
    using namespace std;
     
    using ll = long long;
    using pii = pair<int, int>;
    template <class T>
    using V = vector<T>;
    template <class T>
    using VV = V<V<T>>;
     
    #define pb push_back
    #define eb emplace_back
    #define mp make_pair
    #define fi first
    #define se second
    #define rep(i, n) rep2(i, 0, n)
    #define rep2(i, m, n) for (int i = m; i < (n); i++)
    #define per(i, b) per2(i, 0, b)
    #define per2(i, a, b) for (int i = int(b) - 1; i >= int(a); i--)
    #define ALL(c) (c).begin(), (c).end()
    #define SZ(x) ((int)(x).size())
     
    constexpr ll TEN(int n) { return (n == 0) ? 1 : 10 * TEN(n - 1); }
     
    template <class T, class U>
    void chmin(T& t, const U& u) {
        if (t > u) t = u;
    }
    template <class T, class U>
    void chmax(T& t, const U& u) {
        if (t < u) t = u;
    }
     
    template <class T, class U>
    ostream& operator<<(ostream& os, const pair<T, U>& p) {
        os << "(" << p.first << "," << p.second << ")";
        return os;
    }
     
    template <class T>
    ostream& operator<<(ostream& os, const vector<T>& v) {
        os << "{";
        rep(i, v.size()) {
            if (i) os << ",";
            os << v[i];
        }
        os << "}";
        return os;
    }
     
    #ifdef LOCAL
    void debug_out() { cerr << endl; }
    template <typename Head, typename... Tail>
    void debug_out(Head H, Tail... T) {
        cerr << " " << H;
        debug_out(T...);
    }
    #define debug(...) \
        cerr << __LINE__ << " [" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
    #define dump(x) cerr << __LINE__ << " " << #x << " = " << (x) << endl
    #else
    #define debug(...) (void(0))
    #define dump(x) (void(0))
    #endif
     
    template <unsigned int MOD>
    struct ModInt {
        using uint = unsigned int;
        using ull = unsigned long long;
        using M = ModInt;
     
        uint v;
     
        ModInt(ll _v = 0) { set_norm(_v % MOD + MOD); }
        M& set_norm(uint _v) {  //[0, MOD * 2)->[0, MOD)
            v = (_v < MOD) ? _v : _v - MOD;
            return *this;
        }
     
        explicit operator bool() const { return v != 0; }
        M operator+(const M& a) const { return M().set_norm(v + a.v); }
        M operator-(const M& a) const { return M().set_norm(v + MOD - a.v); }
        M operator*(const M& a) const { return M().set_norm(ull(v) * a.v % MOD); }
        M operator/(const M& a) const { return *this * a.inv(); }
        M& operator+=(const M& a) { return *this = *this + a; }
        M& operator-=(const M& a) { return *this = *this - a; }
        M& operator*=(const M& a) { return *this = *this * a; }
        M& operator/=(const M& a) { return *this = *this / a; }
        M operator-() const { return M() - *this; }
        M& operator++(int) { return *this = *this + 1; }
        M& operator--(int) { return *this = *this - 1; }
     
        M pow(ll n) const {
            if (n < 0) return inv().pow(-n);
            M x = *this, res = 1;
            while (n) {
                if (n & 1) res *= x;
                x *= x;
                n >>= 1;
            }
            return res;
        }
     
        M inv() const {
            ll a = v, b = MOD, p = 1, q = 0, t;
            while (b != 0) {
                t = a / b;
                swap(a -= t * b, b);
                swap(p -= t * q, q);
            }
            return M(p);
        }
     
        bool operator==(const M& a) const { return v == a.v; }
        bool operator!=(const M& a) const { return v != a.v; }
        friend ostream& operator<<(ostream& os, const M& a) { return os << a.v; }
        static uint get_mod() { return MOD; }
    };
     
    using Mint = ModInt<998244353>;
     
    int main() {
        int N, K;
        cin >> N >> K;
        V<pii> rng;
     
        rep(i, K) {
            int l, r;
            cin >> l >> r;
            r++;
            rng.eb(l, r);
        }
     
        V<Mint> dp(N);
        dp[0] = 1;
        dp[1] = -1;
     
        rep(i, N) {
            if (i > 0) dp[i] += dp[i - 1];
            rep(j, K) {
                int l, r;
                tie(l, r) = rng[j];
                if (i + l < N) dp[i + l] += dp[i];
                if (i + r < N) dp[i + r] -= dp[i];
            }
        }
        cout << dp[N - 1].v << endl;
     
        return 0;
    }

Measured memory_bytes: 3976