#include <bits/stdc++.h>
using namespace std;
using std::cout;
using std::cin;
using std::endl;
using ll=long long;
using ld=long double;
const ll ILL=2167167167167167167;
const int INF=2100000000;
#define rep(i,a,b) for (int i=(int)(a);i<(int)(b);i++)
#define all(p) p.begin(),p.end()
template<class T> using _pq = priority_queue<T, vector<T>, greater<T>>;
template<class T> ll LB(vector<T> &v,T a){return lower_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> ll UB(vector<T> &v,T a){return upper_bound(v.begin(),v.end(),a)-v.begin();}
template<class T> bool chmin(T &a,T b){if(a>b){a=b;return 1;}else return 0;}
template<class T> bool chmax(T &a,T b){if(a<b){a=b;return 1;}else return 0;}
template<class T> void So(vector<T> &v) {sort(v.begin(),v.end());}
template<class T> void Sore(vector<T> &v) {sort(v.begin(),v.end(),[](T x,T y){return x>y;});}
bool yneos(bool a,bool upp=0){if(a){cout<<(upp?"YES\n":"Yes\n");}else{cout<<(upp?"NO\n":"No\n");}return a;}
template<class T> void vec_out(vector<T> &p,int ty=0){
    if(ty==2){cout<<'{';for(int i=0;i<(int)p.size();i++){if(i){cout<<",";}cout<<'"'<<p[i]<<'"';}cout<<"}\n";}
    else{if(ty==1){cout<<p.size()<<"\n";}for(int i=0;i<(int)(p.size());i++){if(i) cout<<" ";cout<<p[i];}cout<<"\n";}}
template<class T> T vec_min(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmin(ans,x);return ans;}
template<class T> T vec_max(vector<T> &a){assert(!a.empty());T ans=a[0];for(auto &x:a) chmax(ans,x);return ans;}
template<class T> T vec_sum(vector<T> &a){T ans=T(0);for(auto &x:a) ans+=x;return ans;}
int pop_count(long long a){int res=0;while(a){res+=(a&1),a>>=1;}return res;}
template<class T> bool inside(T l,T x,T r){return l<=x&&x<r;}

#include <atcoder/modint>
using mint = atcoder::modint998244353;

void solve();
// CYAN / FREDERIC
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);

    int t = 1;
    // cin >> t;
    rep(i, 0, t) solve();
}

void solve(){
    int N;
    cin >> N;
    vector<int> L(N), R(N);
    vector<mint> pro(N);
    rep(i, 0, N) cin >> L[i] >> R[i], L[i]--, pro[i] = (mint)(1) / (mint)(R[i] - L[i]);
    rep(i, 0, N) assert((mint)(R[i] - L[i]) != 0);
    mint sum = N;
    mint deg = 0;
    vector<pair<int, int>> q(N * 2);
    rep(i, 0, N){
        q[i * 2 + 1] = {L[i], i};
        q[i * 2] = {R[i], i};
    }
    sort(all(q), [&](pair<int, int> l, pair<int, int> r){
        if (l.first == r.first){
            return l.second > r.second;
        }
        return l.first < r.first;
    });
    bool one = 0;
    mint ans = 0;
    int f = 0;
    for (auto x : q){
        if (one){
            ans += (sum - deg + sum - deg * (x.first - f)) * (x.first - f) / 2;
        }
        sum -= deg * (x.first - f);
        f = x.first;
        if (x.second){
            if (L[x.second] == x.first){
                deg += pro[x.second];
            }
            else{
                deg -= pro[x.second];
            }
        }
        else{
            one ^= 1;
        }
    }
    cout << (ans * pro[0]).val() << "\n";
}