#include <bits/stdc++.h>
using namespace std;

using ll = long long;
#define int ll
#define fi first
#define se second
#define pb push_back
typedef long double ld;
#define double  ld

const int N = 6;
const int M = 10;

int a[100];

vector<pair<int, int> > q;

double brute(int i, int n)
{
    if (i == n+1)
    {
        int mx = 0;
        int mn = 1e9;
        for (auto [l, r] : q)
        {
            int s = 0;
            for (int i=l; i<=r; i++)
                s += a[i];
            mx = max(mx, s);
            mn = min(mn, s);
        }
        if (mn == 0)
            return 1e9;
        return mx*1.0/mn;
    }

    double ans = 1e9;
    for (a[i]=0; a[i]<=M; a[i]++)
        ans = min(ans, brute(i+1, n));
    return ans;
}
double brute2(int n)
{
    double ans = 1;
    int m = q.size();
    for (int i=1; i<(1<<m); i++)
        for (int j=1; j<(1<<m); j++)
            if ((i&j)==0)
        {
            vector<int> a(n+1, 0);
            int c1 = 0;
            int c2 = 0;
            for (int r=0; r<m; r++)
                if ((j>>r)&1)
                {
                    c2++;
                    for (int t=q[r].fi; t<=q[r].se; t++)
                        a[t]--;
                }
            bool ok = true;
            for (int i=1; i<=n; i++)
                if (a[i] < -2)
                    ok = false;
//            int mn = 1e9;
//            int mx = -1;
//            for (int i=1; i<=n; i++)
//                if (a[i] == -2)
//                    mn = min(mn, i), mx = max(mx, i);
//            if (mx != -1)
//                for (int i=mn; i<=mx; i++)
//                    a[i] = -2;

            for (int r=0; r<m; r++)
                if ((i>>r)&1)
                {
                    for (int t=q[r].fi; t<=q[r].se; t++)
                        a[t]++;
                    c1++;
                }
            for (int i=1; i<=n; i++)
                if (a[i] < 0)
                    ok = false;
            if (ok)
                ans = max<double>(ans, c2*1.0/c1);
        }
    return ans;
}

/*
2 2
3 3
4 4
5 5
6 6

1 2
2 3
3 4
4 5
5 6

1 4
2 5
3 6

1 1
2 2
3 3
4 4
5 5
6 6

1 2
2 3
3 4
4 5
*/
int cover[12060];
int fit[12060];
int fit1[12060];
void relax(vector<pair<int, int> >& v)
{
    vector<pair<int, int> > u;
    for (auto [l, r] : v)
        if (u.size() == 0 || u.back().se < r)
            u.pb({l, r});
    v = u;
}
const int mod = 998244353;
int bpow(int a, int b)
{
    int r = 1;
    while (b > 0)
    {
        if (b&1)
            r = r*a%mod;
        a = a*a%mod;
        b/=2;
    }
    return r;
}

int ANS1=0;
vector<int> ANS;
double ask(int n, vector<pair<int, int> >& v, bool FIRST = true)
{
//    cout<<v.size()<<endl;
//    for (auto [l, r] : v)
//        cout<<l<<" "<<r<<endl;
//    cout<<endl;

    if (v.empty())
        return 0;

    vector<pair<int, int> > u;
    int a = 0;
    if (FIRST)
    {
        relax(v);
        for (auto [l, r] : v)
        {
            int c = 0;
            while (true)
            {
                if (fit[l] > r+1)
                    break;
                l = fit[l];
                c++;
            }
            if (c < a)
                continue;
            if (c > a)
            {
                a = c, u.clear();
            }
            if (l<=r)
                u.pb({l, r});
        }
        for (auto [l, r] : v)
        {
            int c = 0;
            while (true)
            {
                if (fit1[r+1] < l-1)
                    break;
                r = fit1[r+1];
                c++;
            }
            if (c < a)
                continue;
            if (c > a)
            {
                a = c, u.clear();
            }
            if (l<=r)
                u.pb({l, r});
        }

    //    for (auto [l, r] : v)
    //        cout<<l<<" "<<r<<" ";
    //    cout<<" -> "<<a<<"\n";

        if (a > 0)
        {
            ANS1 = a;
            sort(u.begin(), u.end());
            relax(u);
    //        cout<<v.size()<<" -> "<<u.size()<<endl;
            double x = ask(n, u, false);
    //        cout<<x<<"\n";
            // s down, xs up
            // 1 down, a up

            return a+x;
        }
    }
//    return 0;

    vector<vector<int> > add(n+2);
    vector<vector<int> > rem(n+2);
    for (auto [l, r] : v)
    {
        add[l].pb(r+1);
        rem[r+1].pb(r+1);
    }

    a = 1e9;
    u.clear();

    multiset<int> ms;
    for (int i=0; i<n; i++)
    {
        for (int j : add[i])
            ms.insert(j);
        for (int j : rem[i])
            ms.erase(ms.find(j));
        if (ms.empty())
            cover[i] = -1;
        else
            cover[i] = *prev(ms.end());
    }
    for (auto [l, r] : v)
    {
//        cout<<l<<" "<<r<<" ";
        int R = fit[l]-1;
        int c = 1;
        while (r < R)
        {
            r = cover[r+1]-1;
            if (r == -1)
                break;
            c++;
        }
        if (r == -1)
            continue;
//        cout<<c<<"\n";
        if (c > a)
            continue;
        if (c < a)
        {
            a = c;
            u.clear();
        }
        if (r > R)
            u.pb({R+1, r});
    }

    add.clear();
    rem.clear();
    add.resize(n+2);
    rem.resize(n+2);
    for (auto [l, r] : v)
    {
        add[r].pb(l-1);
        rem[l-1].pb(l-1);
    }

    a = 1e9;
    u.clear();

    for (int i=n-1; i>=0; i--)
    {
        for (int j : add[i])
            ms.insert(j);
        for (int j : rem[i])
            ms.erase(ms.find(j));
        if (ms.empty())
            cover[i] = 1e9;
        else
            cover[i] = *ms.begin();
    }
    for (auto [l, r] : v)
    {
//        cout<<l<<" "<<r<<" ";
        int L = fit1[r+1]+1;
        int c = 1;
        while (l > L)
        {
            l = cover[l-1]+1;
            if (l > 2*n)
                break;
            c++;
        }
        if (l > 2*n)
            continue;
//        cout<<c<<"\n";
        if (c > a)
            continue;
        if (c < a)
        {
            a = c;
            u.clear();
        }
        if (l < L)
            u.pb({l, L-1});
    }

    if (a < 1e8)
    {
        sort(u.begin(), u.end());
        relax(u);
        double r = (1+ask(n, u))/a;
        ANS.pb(a);
        return r;
    }
    else
        return 0;
}

double smart()
{
    int C = 0;
    map<int, int> mp;
    {
        vector<int> v;
        for (auto [l, r] : q)
        {
            v.pb(l), v.pb(r), v.pb(l-1), v.pb(r+1);
            v.pb(l+1), v.pb(r-1);
        }
        sort(v.begin(), v.end());
        for (int i : v)
        {
            if (mp.count(i))
                continue;
            mp[i] = C++;
        }
    }
    int n = C;

    vector<pair<int, int> > v;
    for (auto [l, r] : q)
    {
        int L = mp[l];
        int R = mp[r];
        v.pb({L, R});
    }
    for (int i=0; i<=n; i++)
        fit[i] = 1e9;
    for (int i=0; i<=n; i++)
        fit1[i] = -1e9;

    for (auto [l, r] : v)
        for (int i=0; i<=l; i++)
            fit[i] = min(fit[i], r+1);
    for (auto [l, r] : v)
        for (int i=r; i<n; i++)
            fit1[i+1] = max(fit1[i+1], l-1);

//    for(int i=0; i<n; i++)
//        cout<<fit[i]<<" ";
//    cout<<"\n";
    sort(v.begin(), v.end());
    return ask(n, v);

//    for(int i=0; i<n; i++)
//        cout<<cover[i]<<" ";
//    cout<<"\n";
//    for(int i=0; i<n; i++)
//        cout<<fit[i]<<" ";
//    cout<<"\n";

//    double ans = 1;
//    for (int i=0; i<n; i++)
//    {
//        int cup = 0;
//        int cdown = 0;
//        int rup = i;
//        int rdown = i;
//        while (true)
//        {
////            cout<<i<<" "<<rdown<<" "<<rup<<" "<<cdown<<" "<<cup<<"\n";
//            if (rup < rdown)
//                rup = cover[rup], cup++;
//            else
//                rdown = fit[rdown], cdown++;
//            if (rup < 0 || rdown > n)
//                break;
//            if (cdown > cup && rup >= rdown)
//                ans = max(ans, cdown*1.0/cup);
//        }
//    }
//
//    return ans;
}

mt19937 rng(time(0));
signed main()
{
//    cout<<fixed<<setprecision(10);
//    int iter = 0;
//	while (true)
//    {
//        iter++;
//        int n = rng()%3+4;
//        int m = rng()%5+5;
////        int n = 5;
////        int m = rng()%5+1;
//        q.clear();
//        for (int i=0; i<m; i++)
//        {
//            int l = rng()%n+1;
//            int r = rng()%n+1;
//            if (l>r) swap(l, r);
//            q.pb({l, r});
//        }
//
//        double x = smart();
//        double y = brute(1, n);
//
//        if (abs(x-y) < 1e-6)
//        {
////            cout<<"@";
//        }
//        else
//        {
//            cout<<"\n";
//            cout<<x<<" "<<y<<"\n";
//            cout<<n<<" "<<m<<"\n";
//            for (int i=0; i<m; i++)
//                cout<<q[i].fi<<" "<<q[i].se<<"\n";
//            exit(0);
//        }
//
//        if (iter%100==0)
//            cout<<iter<<"\n";
//    }

	cin.tie(0)->sync_with_stdio(0);
	cin.exceptions(cin.failbit);

//    cout<<bpow(2, mod-2)<<"\n";
//    return 0;

	int t;
	cin>>t;
	while (t--)
    {
        int n, m;
        cin>>n>>m;
        q.resize(m);
        for (auto& [l, r] : q)
            cin>>l>>r;
        ANS1 = 0;
        ANS.clear();
//        cout<<smart()<<"\n";
//        cout<<"ANS "<<ANS1<<" : ";
//        for (int i : ANS) cout<<i<<" ";
//        cout<<"\n";
        smart();
        int R = 0;
        reverse(ANS.begin(), ANS.end());
        if (ANS.size() > 0)
        {
            for (int i : ANS)
            {
                R = (R + 1)*bpow(i, mod-2)%mod;
            }
        }
        cout<<(R+ANS1+mod)%mod<<"\n";
    }
}
/*
1.0000000000 1.5000000000
4 8
1 3
3 4
2 4
2 3
1 2
1 1
2 4
1 3

1.0000000000 1.5000000000
4 5
1 2
3 4
2 4
1 3
2 3

4
3 3
1 3
2 3
1 2
12 6
2 3
5 7
1 9
4 8
1 2
7 11
4 5
3 4
2 3
1 2
4 4
1 1
6 7
1 3
1 4
2 4
2 5
3 5
3 6
4 6

*/