rt，悬赏一关注

#include<iostream>
#include<cmath>
#include<iomanip>
using namespace std;
unsigned long long t,n,m,maxx,a[5000001],ans;
int main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin >> t >> maxx;
	a[0] = 1;
	for(int i = 1;i <= maxx;i++)a[i] = (a[i - 1] * i) % 998244353;
	while(t--){
		cin >> n >> m;
		if(n < m)ans ^= 0;
		else ans ^= ((a[n] / a[n - m] / a[m]) % 998244353);
	}
	cout << ans % 998244353;
}