import java.util.*;
public class Main{
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int k = sc.nextInt();
		int mod = 998244353;
		
		int[] l = new int[k];
		int[] r = new int[k];
		long[] sum = new long[k];
		for(int i = 0; i < k; i++){
			l[i] = sc.nextInt();
			r[i] = sc.nextInt();
		}
		
		long[] dp = new long[n*2];
		dp[1] = 1;
		
		for(int i = 1; i <= n; i++){
			for(int j = 0; j < k; j++){
				int ra = Math.min(n, i - l[j]);
				ra = Math.max(0, ra);
				int la = Math.max(0, i - r[j]);
				la = Math.min(n, la);
				
				sum[j] += dp[ra];
				dp[i] += sum[j];
				sum[j] -= dp[la];
			}
			dp[i] %= mod;
		}
		System.out.println(dp[n]);
	}
}