//#define _GLIBCXX_DEBUG
//#pragma GCC optimize "trapv"
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

using namespace std;
using namespace __gnu_pbds;

// #pragma GCC target ("avx2")
// #pragma GCC optimization ("O3")
// #pragma GCC optimization ("unroll-loops")
// #pragma optimization_level 3
// #pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math,O3")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")


#define pb push_back 
#define f first
#define s second
#define min3(a, b, c) min(min(a, b), c)
#define max3(a, b, c) max(max(a, b), c)
#define all(v) v.begin(), v.end()

typedef long long ll;
typedef double ld;
typedef long double lld;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<pii> vpi;
typedef vector<pll> vpl;

template <class T> using ordered_set = tree <T, null_type, less <T>, rb_tree_tag, tree_order_statistics_node_update>;

const int INF = 1e9;
//const ll INF = 1e18;
//const ll mod = 1000000007;
const ll mod = 998244353;

void solve(int tc){
    int n, k;
    cin >> n >> k;
    vpi s(k);

    for(int i = 0; i < k; i++){
        cin >> s[i].f >> s[i].s;
    }

    vl pref_sum(n+1, 0), dp(n+1, 0);
    sort(all(s));
    dp[0] = 0; 
    dp[1] = 1;
    pref_sum[0] = 0;
    pref_sum[1] = 1;

    for(int i = 2; i <= n; i++){
        for(pii x : s){
            if(i - x.s > 0)
                (dp[i] += pref_sum[i-x.f] - pref_sum[i-x.s-1]) %= mod;
            else if(i - x.f >= 0)
                for(int j = i-x.f; j >= 0; --j)
                    (dp[i] += dp[j]) %= mod;
            else break;
        }
        (pref_sum[i] = pref_sum[i-1] + dp[i]) %= mod;   
    }


    cout << dp[n] << "\n";
}

int main(){
    ios_base::sync_with_stdio(NULL);
    cin.tie(NULL);
    
    int tc = 1;
    //cin >> tc;
    for (int t = 0; t < tc; t++) solve(t);

    return 0;
}