#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<iostream>
#include<cstdint>
#include<cstddef>
#include<vector>
using namespace std;
using i32 = int_fast32_t;
using i64 = int_fast64_t;
using usize = uint_fast64_t;
#define rep(i, n) for (usize i = 0; i < (usize)(n); i++)
#define all(a) (a).begin(),(a).end()
#define rall(a) (a).rbegin(),(a).rend()
using P = pair<i64,i64>;
constexpr i64 MAX = 10000000;
constexpr i64 MOD = 998244353;
i64 fac[MAX], finv[MAX], inv[MAX];

template<i64 modulus>
class modcal {

public:
    i64 a;

    constexpr modcal(const i64 x = 0) noexcept: a(x % modulus) {}

    constexpr i64 &value() noexcept { return a; }

    constexpr const i64 &value() const noexcept { return a; }

    constexpr modcal operator+(const modcal rhs) const noexcept {
        return modcal(*this) += rhs;
    }

    constexpr modcal operator-(const modcal rhs) const noexcept {
        return modcal(*this) -= rhs;
    }

    constexpr modcal operator*(const modcal rhs) const noexcept {
        return modcal(*this) *= rhs;
    }

    constexpr modcal operator/(const modcal rhs) noexcept {
        return modcal(*this) /= rhs;
    }

    constexpr modcal &operator+=(const modcal rhs) noexcept {
        a += rhs.a;
        if (a >= modulus) {
            a -= modulus;
        }
        return *this;
    }

    constexpr modcal &operator-=(const modcal rhs) noexcept {
        if (a < rhs.a) {
            a += modulus;
        }
        a -= rhs.a;
        return *this;
    }

    constexpr modcal &operator*=(const modcal rhs) noexcept {
        a = a * rhs.a % modulus;
        return *this;
    }

    constexpr modcal &operator/=(modcal rhs) noexcept {
        i64 exp = modulus - 2;
        while (exp) {
            if (exp % 2) {
                *this *= rhs;
            }
            rhs *= rhs;
            exp /= 2;
        }
        return *this;
    }

    void COMninit() {
        fac[0] = fac[1] = 1;
        finv[0] = finv[1] = 1;
        inv[1] = 1;
        for (int i = 2; i < MAX; i++) {
            fac[i] = fac[i - 1] * i % modulus;
            inv[i] = MOD - inv[modulus % i] * (modulus / i) % modulus;
            finv[i] = finv[i - 1] * inv[i] % modulus;
        }
    }

    i64 COMn(i64 n, i64 k) {
        if (n < k)
            return 0;
        if (n < 0 || k < 0)
            return 0;
        return fac[n] * (finv[k] * finv[n - k] % modulus) % modulus;
    }

    constexpr modcal<998244353> modpow(const modcal<998244353> &a, i64 n) {
        if (n == 0)
            return 1;
        auto t = modpow(a, n / 2);
        t = t * t;
        if (n & 1)
            t = t * a;
        return t;
    }

    i64 modinv(i64 x) {//xy = 1となるyのうちMOD以下になるものを返す
        i64 m = MOD;
        i64 u = 1, v = 0;
        while (m) {
            i64 t = x / m;
            x -= t * m;
            swap(x, m);
            u -= t * v;
            swap(u, v);
        }
        u %= MOD;
        if (u < 0) u += MOD;
        return u;
    }
};

using modc = modcal<998244353>;

int main(){
ios::sync_with_stdio(false);
std::cin.tie(nullptr);
i64 n,k;
cin >> n >> k;
vector<i32> l(k),r(k);
rep(i,k){
    cin >> l[i] >> r[i];
}
vector<modc> dp(n + 1,0);
dp[1] = 1;
vector<modc> imos(n + 1,0);
for(i32 i = 1; i <= n; i++){
   imos[i] = imos[i] + imos[i - 1];
   dp[i] = dp[i] + imos[i];
   rep(j,k){
       if(l[j] + i <= n)imos[l[j] + i] = imos[l[j] + i] + dp[i];
       if(r[j] + i + 1<= n)imos[r[j] + i + 1] = imos[r[j] + i + 1] - dp[i];
   }
}
cout << dp[n].a << endl;
}

Measured memory_bytes: 6336