#include <bits/stdc++.h>

using namespace std;

int32_t main() {

    ios_base::sync_with_stdio(false);

    cin.tie(0);

    long long n;

    cin >> n;

    long long k;

    cin >> k;

    long long diff[4*200005];

    memset(diff,0,sizeof diff);

    vector<pair<long long,long long> > v;

    for(long long i = 0 ; i < k ; i++) {

        long long x;

        cin >> x;

        long long y;

        cin >> y;

        v.push_back({x,y});

    }

    diff[0]=0;

    diff[1]=1;

    long long last=0;

    for(long long i=1; i<=n+5; i++) {

        if(i>2) {

            diff[i]+=diff[i-1];

        }

        long long cur = diff[i]%998244353;

        for(long long j=0; j<v.size(); j++) {

            diff[i+v[j].first]+=cur;

            diff[i+v[j].second+1]-=cur;

        }

    }

    cout << diff[n]%998244353 << '\n';

    return 0;

}