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

const int md = 998244353;

inline int mul(int x, int y) {
	return 1ull * x * y % md;
}

inline int fpow(int x, int y) {
	int ans = 1;
	while (y) {
		if (y & 1) ans = mul(ans, x);
		y >>= 1; x = mul(x, x);
	}
	return ans;
}

const int N = 2005;

int l[N], r[N], b[N];
int T, n, m, ans1, ans2;

namespace dcx {

const int N = 1005, M = 10005;
const double eps = 1e-8;

double a[M][N];
int id[N + M];
int n, m;

void pivot(int r, int c) {
    swap(id[r + n], id[c]);
    double tmp = -a[r][c]; a[r][c] = -1;
    for (int i = 0; i <= n; i++) a[r][i] /= tmp;
    for (int i = 0; i <= m; i++) {
        if (i != r && fabs(a[i][c]) > eps) {
            tmp = a[i][c]; a[i][c] = 0;
            for (int j = 0; j <= n; j++) a[i][j] += tmp * a[r][j];
        }
    }
}

double simplex() {
	memset(id, 0, sizeof(id)); a[0][0] = 0;
    for (int i = 1; i <= n; i++) id[i] = i;
    while (1) {
        int r = -1;
        for (int i = 1; i <= m; i++) {
            if (a[i][0] < -eps) {
                if (r == -1 || a[i][0] < a[r][0]) {
                    r = i;
                }
            }
        }
        if (r == -1) break;
        int c = -1;
        for (int i = 1; i <= n; i++)  {
            if (a[r][i] > eps) {
                c = i;
                break;
            }
        }
        assert(c != -1);
        pivot(r, c);
    }
    while (1) {
        int c = -1;
        for (int i = 1; i <= n; i++) {
            if (a[0][i] > eps) {
                c = i;
                break;
            }
        }
        if (c == -1) break;
        int r = -1; double lim;
        for (int i = 1; i <= m; i++) {
            if (a[i][c] < -eps) {
                double now = a[i][0] / -a[i][c];
                if (r == -1 || now < lim) {
                    lim = now;
                    r = i;
                }
            }
        }
        assert(r != -1);
        pivot(r, c);
    }
    return a[0][0];
}

}

int main() {
	scanf("%d", &T);
	while (T--) {
		scanf("%d%d", &n, &m);
		for (int i = 1; i <= m; i++) {
			scanf("%d%d", &l[i], &r[i]);
			b[i] = l[i];
		}
		sort(b + 1, b + m + 1);
		dcx::m = m * 2;
		dcx::n = m + 1;
		for (int i = 1; i <= m; i++) dcx::a[0][i] = 0;
		dcx::a[0][m + 1] = -1;
		for (int i = 1; i <= m; i++) {
			l[i] = lower_bound(b + 1, b + m + 1, l[i]) - b;
			r[i] = upper_bound(b + 1, b + m + 1, r[i]) - b - 1;
			memset(dcx::a[i * 2 - 1], 0, sizeof(dcx::a[i * 2 - 1]));
			memset(dcx::a[i * 2], 0, sizeof(dcx::a[i * 2 - 1]));
			for (int j = l[i]; j <= r[i]; j++) {
				dcx::a[i * 2 - 1][j] = 1;
				dcx::a[i * 2][j] = -1;
			}
			dcx::a[i * 2 - 1][0] = -1;
			dcx::a[i * 2][m + 1] = 1;
		}
		double res = -dcx::simplex();
		// fprintf(stderr, "res = %.6lf\n", res);
		int ok = 0, ans = 0;
		for (int i = 1; i <= m; i++) {
			for (int j = 1; j <= i; j++) {
				if (fabs((double)i / j - res) < 1e-8) {
					ans = mul(i, fpow(j, md - 2)); ok = 1;
					break;
				}
			}
			if (ok) break;
		}
		printf("%d\n", ans);
	}
	return 0;
}

/*
3
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
*/