#include <bits/stdc++.h>
using namespace std;
const int N = 4010,mod = 998244353;
int T,n,m,k,cnt,p[N],L[N],R[N],dis[N];
vector <pair <int,int>> v[N];
struct Frac{int p,q;} ans[N];
bool operator < (Frac x,Frac y){return x.p * y.q < x.q * y.p;}
int ksm(int x,int y)
{
	int ret = 1;
	while(y)
	{
		if(y & 1) ret = 1LL * ret * x % mod;
		x = 1LL * x * x % mod,y >>= 1;
	}
	return ret;
}
bool check(Frac x)
{
	for(int i = 1;i <= k;i++) v[i].clear();
	for(int i = 2;i <= k;i++) v[i].push_back(make_pair(i - 1,0));
	for(int i = 1;i <= m;i++)
	{
		v[R[i]].push_back(make_pair(L[i],-x.q));
		v[L[i]].push_back(make_pair(R[i],x.p));
	}
	memset(dis,0x3f,sizeof(dis));
	dis[0] = 0;
	for(int i = 1;i <= k;i++)
		for(int x = 1;x <= k;x++)
			for(pair <int,int> p : v[x])
				dis[p.first] = min(dis[p.first],dis[x] + p.second);
	for(int x = 1;x <= k;x++)
		for(pair <int,int> p : v[x])
			if(dis[p.first] > dis[x] + p.second)
				return false;
	return true;
}
int main()
{
	scanf("%d",&T);
	while(T--)
	{
		scanf("%d%d",&n,&m);
		k = 0;
		for(int i = 1;i <= m;i++)
		{
			scanf("%d%d",&L[i],&R[i]);
			p[++k] = --L[i],p[++k] = R[i];
		}
		sort(p + 1,p + k + 1);
		k = unique(p + 1,p + k + 1) - p - 1;
		for(int i = 1;i <= m;i++)
		{
			L[i] = lower_bound(p + 1,p + k + 1,L[i]) - p;
			R[i] = lower_bound(p + 1,p + k + 1,R[i]) - p;
		}
		ans[cnt = 1] = (Frac){1,1};
		for(int i = 2;i <= m;i++)
			for(int j = 1;j < i;j++)
				ans[++cnt] = (Frac){i,j};
		sort(ans + 1,ans + cnt + 1);
		int l = 0,r = cnt,mid;
		while(r - l > 1)
		{
			mid = (l + r) / 2;
			if(check(ans[mid])) r = mid;
			else l = mid;
		}
		printf("%lld\n",1LL * ans[r].p * ksm(ans[r].q,mod - 2) % mod);
	}
	return 0;
}