#include <bits/stdc++.h>
using namespace std;
const int mod=998244353;
int n,k;
int l[200005],r[200005];
 
int dp[2000005];
 
int main() {
  scanf("%d %d",&n,&k);
  for(int i=1;i<=k;i++) {
    scanf("%d %d",&l[i],&r[i]);
  }
  dp[1]=1;
  dp[2]=-1;
  for(int i=1;i<=n;i++) {
    dp[i]=(dp[i]+dp[i-1])%mod;
    for(int j=1;j<=k;j++) {
      dp[i+l[j]]=(dp[i+l[j]]+dp[i])%mod;
      dp[i+r[j]+1]=(dp[i+r[j]+1]-dp[i]+mod)%mod;
    }
  }
  printf("%d",dp[n]);
  return 0;
}