#define MD 998244353
using mm = Mint;

ll @N; int @K, @m;

VI bst(K + 1, -1); // bst[r] := \max_{R_i = r} L_i
VI g(K + 1, -1); // g[r] := \max_{R_i <= r} L_i

rep(m) {
	int @L, @R;
	bst[R] >?= L;
}

rep(i, 1, K + 1) g[i] = max(bst[i], g[i - 1]); // bst[i] 前缀最大刚好是 g[i]

vector<vector<mm>> f(K + 1, vector<mm>(K + 1, 0)), pre(K + 1, vector<mm>(K + 1, 0));
f[0][0] = 1;

pre[0][0] = 1;
rep(i, 1, K + 1) pre[0][i] = pre[0][i - 1] + f[0][i];

rep(s, 1, K + 1) {
	rep(x, 1, K + 1) {
		f[s][x] = pre[s - 1][x - 1];
		if(g[x - 1] > 0) f[s][x] -= pre[s - 1][g[x - 1] - 1];
	}
	rep(x, 1, K + 1) pre[s][x] = pre[s][x - 1] + f[s][x];
}

vector<mm> H(K + 1, 0);
rep(s, 1, K + 1) rep(x, g[K], K + 1) H[s] += f[s][x];

vector<mm> F(K + 1, 0); // F(N, s) = s! * {N, s}

Comb<mm> comb;

rep(s, 1, K + 1) {

	rep(j, s + 1) {
		mm tt = 1;
		tt *= (-1) ** (s - j);
		tt *= comb.C(s, j);
		tt *= powmod(j, N, MD);
		F[s] += tt;
	}

}

mm ans = 0;
rep(s, K + 1) ans += H[s] * F[s];
wt(ans);