#include <bits/stdc++.h>
using namespace std;
const int INF = 0x3f3f3f3f, MOD = 998244353;

int inv(int x) {
    int t = MOD - 2, ret = 1;
    while(t > 0) {
        if(t & 1) ret = 1LL * ret * x % MOD;
        x = 1LL * x * x % MOD;
        t >>= 1;
    }
    return ret;
}

int n, m, l[2005], r[2005], f[4005][4005];
vector<int> hv, hvr[4005];
void trans(int fr[], int to[]) {
    for(int i = 0; i < m; i++) to[i] = INF;
    for(int i = 0; i < n; i++) to[l[i]] = min(to[l[i]], fr[r[i]]);

    for(int i = m - 2; i >= 0; i--) to[i] = min(to[i], to[i + 1]);
    for(int i = 0; i < m; i++)
        for(auto j : hvr[i]) for(int k = j; to[k] > to[i] + 1; k--) to[k] = to[i] + 1;
}
bool cmp(const pair<int, int>& u, const pair<int, int>& v) {
    return u.first * v.second < u.second * v.first;
}

void solve() {
    scanf("%*d%d", &n);
    hv.clear();
    for(int i = 0; i < n; i++) {
        scanf("%d%d", &l[i], &r[i]);
        hv.push_back(l[i]);
        hv.push_back(r[i] + 1);
    }
    sort(hv.begin(), hv.end());
    hv.resize(unique(hv.begin(), hv.end()) - hv.begin());
    m = hv.size();
    for(int i = 0; i < n; i++) {
        l[i] = lower_bound(hv.begin(), hv.end(), l[i]) - hv.begin();
        r[i] = upper_bound(hv.begin(), hv.end(), r[i]) - hv.begin();
    }

    for(int i = 0; i < m; i++) hvr[i].clear();
    for(int i = 0; i < n; i++) hvr[l[i]].push_back(r[i]);

    for(int i = 0; i < m; i++) f[0][i] = 0;
    for(int i = 1; i <= m; i++) trans(f[i], f[i + 1]);

    pair<int, int> ans = make_pair(m, 1);
    for(int i = 0; i < m; i++) if(f[m][i] < INF / 2) {
        pair<int, int> now = make_pair(-m, 1);
        for(int j = 0; j < m; j++) if(f[j][i] < INF / 2) {
            pair<int, int> upd = make_pair(f[m][i] - f[j][i], m - j);
            if(cmp(now, upd)) now = upd;
        }
        if(cmp(now, ans)) ans = now;
    } 
    int ret = 1LL * ans.second * inv(ans.first) % MOD;
    printf("%d\n", ret);
}

int main() {
    int T;
    scanf("%d", &T);
    while(T--) solve();
    return 0;
}