G求调

#include <bits/stdc++.h>

#define int long long

using namespace std;

const int N = 5e5 + 5, mod = 998244353;

int diff[N], w[N], dp[N];

signed main()
{
	int n, m;
	cin >> n >> m;
	for (int i = 0; i < m; i ++ )
	{
		int l, r;
		scanf("%lld%lld", &l, &r);
		if (l <= r - 1) diff[l] = diff[l] + 1, diff[r] = diff[r] - 1;
	}
	int cur = 0;
	for (int i = 1; i < n; i ++ ) cur += diff[i], w[i] = cur;
	dp[0] = 1;
	if (n >= 1) dp[1] = 1;
	for (int i = 2; i <= n; i ++ ) dp[i] = (dp[i - 1] + dp[i - 2] * w[i - 1] % mod) % mod;
	cout << dp[n] << endl;
	return 0;
}
//问题是可能会有四个颜色一样连续的块