#include <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <tuple>
#include <cmath>
#include <numeric>
#include <functional>
#include <cassert>
#include <atcoder/modint>
#include <atcoder/segtree>
#include <atcoder/lazysegtree>

#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }

using namespace std;
typedef long long ll;

template<typename T>
vector<vector<T>> vec2d(int n, int m, T v){
    return vector<vector<T>>(n, vector<T>(m, v));
}

template<typename T>
vector<vector<vector<T>>> vec3d(int n, int m, int k, T v){
    return vector<vector<vector<T>>>(n, vector<vector<T>>(m, vector<T>(k, v)));
}

template<typename T>
void print_vector(vector<T> v, char delimiter=' '){
    if(v.empty()) {
        cout << endl;
        return;
    }
    for(int i = 0; i+1 < v.size(); i++) cout << v[i] << delimiter;
    cout << v.back() << endl;
}


using mint = atcoder::modint998244353;

ostream& operator<<(ostream& os, const mint& m){
    os << m.val();
    return os;
}

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

S op(S x, S y){
    return S(x.cnt+y.cnt, x.sum+y.sum);
}

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

S mapping(mint f, S x){
    return S(x.cnt, f*x.cnt+x.sum);
}

mint composition(mint f, mint g){
    return f+g;
}

mint id(){
    return mint(0);
}

using Seg = atcoder::lazy_segtree<S, op, e, mint, mapping, composition, id>;

template<typename T>
class Cumsum{
    public:
    Cumsum(vector<T> v): v(v){
        n = v.size();
        v_cumsum = vector<T>(n+1, T(0));
        for(int i = 0; i < n; i++) v_cumsum[i+1] = v_cumsum[i]+v[i];
    }
    /**
     * v[l] + ... + v[r-1]
     */ 
    T sum(int l, int r){
        if(r <= l) return T(0);
        if(r > n) r = n;
        if(l < 0) l = 0;
        return v_cumsum[r]-v_cumsum[l];
    }
    private:
    int n;
    vector<T> v;
    vector<T> v_cumsum;
};

template<typename T>
class Compress{
    public:
    vector<T> data;
    int offset;
    Compress(vector<T> data_, int offset=0): offset(offset){
        data = data_;
        sort(begin(data), end(data));
        data.erase(unique(begin(data), end(data)), end(data));
    };
    int operator[](T x) {
        auto p = lower_bound(data.begin(), data.end(), x);
        assert(x == *p);
        return offset+(p-data.begin());
	}
    T inv(int x){
        return data[x-offset];
    }
    int size(){
        return data.size();
    }
};

#define N_MAX 200002
mint inv[N_MAX],fac[N_MAX],finv[N_MAX];

void init(){
    const ll MOD = mint::mod();
    fac[0]=1;fac[1]=1;
    finv[0]=1;finv[1]=1;
    inv[1]=1;
    for(int i=2;i<N_MAX;i++){
        inv[i]=mint(MOD)-inv[MOD%i]*(MOD/i);
        fac[i]=fac[i-1]*(ll) i;
        finv[i]=finv[i-1]*inv[i];
    }
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << setprecision(10) << fixed;
    init();
    int n; cin >> n;
    vector<int> b(n), c(n);
    vector<int> u;
    for(int i = 0; i < n; i++){
        cin >> b[i] >> c[i]; b[i]--;
        u.push_back(b[i]);
        u.push_back(c[i]);
    }
    auto cp = Compress<int>(u);
    int m = cp.size();
    vector<int> len(m-1);
    vector<S> s;
    for(int i = 0; i < m-1; i++){
        len[i] = cp.data[i+1]-cp.data[i];
        s.push_back(S(len[i], mint(0)));
    }
    Seg seg(s);
    for(int i = 0; i < n; i++){
        int l = cp[b[i]];
        int r = cp[c[i]];
        int len = c[i]-b[i];
        mint p = mint(len).inv();
        seg.apply(l, r, p);
    }
    mint ans = mint(n)*mint(n-1);
    for(int i = 0; i < n; i++){
        int l = cp[b[i]];
        int r = cp[c[i]];
        int len = c[i]-b[i];
        mint p = mint(len).inv();
        mint tmp = seg.prod(l, r).sum*p;
        tmp -= p;
        ans -= tmp;
    }
    ans *= fac[n]/4;
    cout << ans << endl;
}