#include<bits/stdc++.h>
using namespace std;
#define lint long long
#define inf 100000000000000000
#define mod 998244353
#define MAX 1000005
#define pb push_back
#define vit vector<int>::iterator
typedef pair<lint,lint> pii;
lint L[MAX],R[MAX],P[MAX],DP[MAX];
int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    lint n,k;
    cin>>n>>k;
    for(lint i=1;i<=k;i++) cin>>L[i]>>R[i];
    DP[n]=1;P[n]=1;
    for(lint i=n-1;i>=1;i--){
        for(lint j=1;j<=k;j++){
            DP[i]=(DP[i]+P[i+L[j]]-P[i+R[j]+1]+mod)%mod;
        }
        P[i]=(P[i+1]+DP[i])%mod;
    }
    cout<<DP[1];
    return 0;
}
