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                (J U S T   L I K E   E V E R Y O N E   E L S E !)

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*/                              
#include<bits/stdc++.h>
using namespace std;
 
#define fastio ios_base::sync_with_stdio(0); cin.tie(0)
#define LL long long 
#define mod 998244353 
#define all(v) v.begin(),v.end()
#define pr(v) pair<v,v>
#define pb push_back
#define FOR(i, j, k) for (auto i=j ; i<k ; i++)
#define ROF(i, j, k) for (auto i=j ; i>=k ; i--) 
#define debug(...) fprintf(stderr, __VA_ARGS__), fflush(stderr)
#define time__(d) for(long blockTime = 0; (blockTime == 0 ? (blockTime=clock()) != 0 : false); debug("%s time : %.4fs", d, (double)(clock() - blockTime) / CLOCKS_PER_SEC))

const long long INF = 1e18;
const long long MAX = 2e5+10;
int main(){
    fastio;
    int t=1;// cin>>t;
    while(t--){
        int n,k; cin>>n>>k;
        vector<pair<int,int>>v(k);
        FOR(i,0,k) cin>>v[i].first>>v[i].second;
        vector<LL>dp(n+1,0);
        vector<LL>p(n+1,0);
        p[1]=1;
        FOR(i,2,n+1) {
            LL pr=0;
            FOR(j,0,k){
                int l=i-v[j].second,r=i-v[j].first;
                if(i<=v[j].first) continue;
                if(i<=v[j].second) l=1;

                LL v = ((p[r]-p[l-1])%mod+mod)%mod;
               // cout<<v<<", ";
                pr = ((pr+v)%mod+mod)%mod;
            }// cout<<"\n";
            dp[i] = pr;
            p[i] = ((pr+p[i-1])%mod+mod)%mod;
        }
        cout<<dp[n];
    }
}


Measured memory_bytes: 6288