#include <algorithm>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <queue>
#include <vector>
using namespace std;

typedef long long ll;

const int N = 2e3 + 5;
const ll inf = 1e6;
const double eps = 1e-12;
const ll mod = 998244353;

int n, m, k;
int l[N], r[N];
vector<int> t;

vector<pair<int, int>> e[N];
double dis[N];
int cnt[N], vis[N];
queue<int> q;

ll fpow(ll x, ll k) {
    ll ans = 1;
    while (k) {
        if (k & 1)
            ans = ans * x % mod;
        x = x * x % mod;
        k >>= 1;
    }
    return ans;
}
bool cmp(pair<int, int> x, pair<int, int> y) {
    return x.first * y.second < x.second * y.first;
}

int check(double mid) {
    for (int i = 0; i <= k; i++) {
        dis[i] = inf;
        cnt[i] = vis[i] = 0;
    }
    dis[0] = 0, vis[0] = 1;
    q.push(0);
    while (!q.empty()) {
        int x = q.front();
        q.pop();
        vis[x] = 0;
        for (auto [y, w] : e[x]) {
            double d = w;
            if (w > 0)
                d = mid;
            if (dis[y] > dis[x] + d) {
                dis[y] = dis[x] + d;
                cnt[y] = cnt[x] + 1;
                if (cnt[y] >= k + 1)
                    return 0;
                if (!vis[y]) {
                    q.push(y);
                    vis[y] = 1;
                }
            }
        }
    }
    return 1;
}

void solve() {
    cin >> n >> m;
    t.clear();
    for (int i = 1; i <= m; i++) {
        cin >> l[i] >> r[i];
        l[i]--;
        t.push_back(l[i]);
        t.push_back(r[i]);
    }
    sort(t.begin(), t.end());
    t.erase(unique(t.begin(), t.end()), t.end());
    for (int i = 1; i <= m; i++) {
        l[i] = lower_bound(t.begin(), t.end(), l[i]) - t.begin() + 1;
        r[i] = lower_bound(t.begin(), t.end(), r[i]) - t.begin() + 1;
    }
    k = t.size();
    for (int i = 0; i <= k; i++)
        e[i].clear();
    for (int i = 2; i <= k; i++)
        e[i].push_back({i - 1, 0});
    for (int i = 1; i <= k; i++)
        e[0].push_back({i, 0});
    for (int i = 1; i <= m; i++) {
        e[r[i]].push_back({l[i], -1});
        e[l[i]].push_back({r[i], 1});
    }

    vector<pair<int, int>> val;
    for (int i = 1; i <= m; i++)
        for (int j = 1; j <= i; j++)
            val.push_back({i, j});
    sort(val.begin(), val.end(), cmp);
    int l = 0, r = val.size() - 1, mid, ans = 0;
    while (l <= r) {
        mid = (l + r) >> 1;
        if (check(1.0 * val[mid].first / val[mid].second)) {
            ans = mid;
            r = mid - 1;
        } else
            l = mid + 1;
    }
    cout << val[ans].first * fpow(val[ans].second, mod - 2) % mod << "\n";
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int T = 1;
    cin >> T;
    while (T--) {
        solve();
    }
    return 0;
}