#include <bits/stdc++.h>
#ifdef LOCAL
#include <debug.hpp>
#else
#define debug(...) void(0)
#endif

#include "atcoder/lazysegtree"
#include "atcoder/modint"

using namespace std;

typedef long long ll;
#define all(x) begin(x), end(x)
constexpr int INF = (1 << 30) - 1;
constexpr long long IINF = (1LL << 60) - 1;
constexpr int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};

template <class T> istream& operator>>(istream& is, vector<T>& v) {
    for (auto& x : v) is >> x;
    return is;
}

template <class T> ostream& operator<<(ostream& os, const vector<T>& v) {
    auto sep = "";
    for (const auto& x : v) os << exchange(sep, " ") << x;
    return os;
}

template <class T, class U = T> bool chmin(T& x, U&& y) { return y < x and (x = forward<U>(y), true); }

template <class T, class U = T> bool chmax(T& x, U&& y) { return x < y and (x = forward<U>(y), true); }

template <class T> void mkuni(vector<T>& v) {
    sort(begin(v), end(v));
    v.erase(unique(begin(v), end(v)), end(v));
}

template <class T> int lwb(const vector<T>& v, const T& x) { return lower_bound(begin(v), end(v), x) - begin(v); }

using mint = atcoder::modint998244353;

struct S {
    mint sum, cnt;
    S(mint sum, mint cnt) : sum(sum), cnt(cnt) {}
};

S op(S l, S r) { return S(l.sum + r.sum, l.cnt + r.cnt); }

S e() { return S(0, 0); }

S mapping(mint l, S r) { return S(r.sum + r.cnt * l, r.cnt); }

mint composition(mint l, mint r) { return l + r; }

mint id() { return 0; }

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int N;
    cin >> N;
    vector<int> B(N), C(N);
    for (int i = 0; i < N; i++) cin >> B[i] >> C[i], B[i]--;

    mint ans = mint(N) * (N - 1) / 4;
    vector<int> cand;
    for (int i = 0; i < N; i++) {
        cand.emplace_back(B[i]);
        cand.emplace_back(C[i]);
    }
    mkuni(cand);
    int sz = cand.size();
    vector<S> init;
    for (int i = 0; i < sz - 1; i++) init.emplace_back(0, cand[i + 1] - cand[i]);
    atcoder::lazy_segtree<S, op, e, mint, mapping, composition, id> seg(init);
    for (int i = 0; i < N; i++) {
        int l = lwb(cand, B[i]), r = lwb(cand, C[i]);
        ans -= seg.prod(l, r).sum / (C[i] - B[i]) / 2;
        seg.apply(l, r, mint(C[i] - B[i]).inv());
    }

    for (int i = 0; i < N; i++) ans *= i + 1;
    cout << ans.val() << '\n';
    return 0;
}