#include <bits/stdc++.h>

using namespace std;

#define overload4(_1, _2, _3, _4, name, ...) name
#define rep1(n) for(int i = 0; i < (int)(n); ++i)
#define rep2(i, n) for(int i = 0; i < (int)(n); ++i)
#define rep3(i, a, b) for(int i = (a); i < (int)(b); ++i)
#define rep4(i, a, b, c) for(int i = (a); i < (int)(b); i += (c))
#define rep(...) overload4(__VA_ARGS__, rep4, rep3, rep2, rep1)(__VA_ARGS__)

#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; --i)
#define ALL(a) (a).begin(), (a).end()
#define Sort(a) (sort((a).begin(), (a).end()))
#define RSort(a) (sort((a).rbegin(), (a).rend()))
#define UNIQUE(a) (a.erase(unique((a).begin(), (a).end()), (a).end()))

typedef long long int ll;
typedef unsigned long long ul;
typedef long double ld;
typedef vector<int> vi;
typedef vector<long long> vll;
typedef vector<char> vc;
typedef vector<string> vst;
typedef vector<double> vd;
typedef vector<long double> vld;
typedef pair<long long, long long> P;

template<class T> long long sum(const T& a){ return accumulate(a.begin(), a.end(), 0LL); }
template<class T> auto min(const T& a){ return *min_element(a.begin(), a.end()); }
template<class T> auto max(const T& a){ return *max_element(a.begin(), a.end()); }

const long long MINF = 0x7fffffffffff;
const long long INF = 0x1fffffffffffffff;
const long long MOD = 998244353;
const long double EPS = 1e-9;
const long double PI = acos(-1);
 
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; }

template<typename T1, typename T2> istream &operator>>(istream &is, pair<T1, T2> &p){ is >> p.first >> p.second; return is; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &p){ os << "(" << p.first << ", " << p.second << ")"; return os; }
template<typename T> istream &operator>>(istream &is, vector<T> &v){ for(T &in : v) is >> in; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &v){ for(int i = 0; i < (int) v.size(); ++i){ os << v[i] << (i + 1 != (int) v.size() ? " " : ""); } return os; }
template <typename T, typename S> ostream &operator<<(ostream &os, const map<T, S> &mp){ for(auto &[key, val] : mp){ os << key << ":" << val << " "; } return os; }
template <typename T> ostream &operator<<(ostream &os, const set<T> &st){ auto itr = st.begin(); for(int i = 0; i < (int)st.size(); ++i){ os << *itr << (i + 1 != (int)st.size() ? " " : ""); itr++; } return os; }
template <typename T> ostream &operator<<(ostream &os, const multiset<T> &st){ auto itr = st.begin(); for(int i = 0; i < (int)st.size(); ++i){ os << *itr << (i + 1 != (int)st.size() ? " " : ""); itr++; } return os; }
template <typename T> ostream &operator<<(ostream &os, queue<T> q){ while(q.size()){ os << q.front() << " "; q.pop(); } return os; }
template <typename T> ostream &operator<<(ostream &os, deque<T> q){ while(q.size()){ os << q.front() << " "; q.pop_front(); } return os; }
template <typename T> ostream &operator<<(ostream &os, stack<T> st){ while(st.size()){ os << st.top() << " "; st.pop(); } return os; }
template <class T, class Container, class Compare> ostream &operator<<(ostream &os, priority_queue<T, Container, Compare> pq){ while(pq.size()){ os << pq.top() << " "; pq.pop(); } return os; }

template<class T, class U> inline T vin(T& vec, U n) { vec.resize(n); for(int i = 0; i < (int) n; ++i) cin >> vec[i]; return vec; }
template<class T> inline void vout(T vec, string s = "\n"){ for(auto x : vec) cout << x << s; }
template<class... T> void in(T&... a){ (cin >> ... >> a); }
void out(){ cout << '\n'; }
template<class T, class... Ts> void out(const T& a, const Ts&... b){ cout << a; (cout << ... << (cout << ' ', b)); cout << '\n'; }
template<class T, class U> void inGraph(vector<vector<T>>& G, U n, U m, bool directed = false){ G.resize(n); for(int i = 0; i < m; ++i){ int a, b; cin >> a >> b; a--, b--; G[a].push_back(b); if(!directed) G[b].push_back(a); } }

struct RandomNumber{
    int64_t seed = chrono::duration_cast<chrono::milliseconds>(chrono::system_clock::now().time_since_epoch()).count();
    uniform_int_distribution<long long> p;
    mt19937_64 rnd;

	RandomNumber(long long l = 0, long long r = 0){
        rnd = mt19937_64(seed);
        p = uniform_int_distribution<long long>(l, r);
    }

	long long get(){
        return p(rnd);
    }
};

ll n;
vll l, r;

void input(){
    in(n);
    l.resize(n);
    r.resize(n);
    rep(i, n) in(l[i], r[i]);
}

void solve(){
    ll mn = min(l), mx = max(r) - (n - 1);
    rep(i, n){
        chmax(mn, l[i] - (n - 1));
        chmin(mx, r[i] + (n - 1));
    }
    if(mn > mx){
        out(0);
        return;
    }

    auto check = [&](ll x){
        priority_queue<ll, vll, greater<>> q;
        vector<vll> mp(n + 1);
        rep(i, n){
            if(l[i] <= x && x <= r[i]){
                q.push(r[i]);
            }
            if(x < l[i] && l[i] <= x + n){
                mp[l[i] - x].push_back(r[i]);
            }
        }

        rep(i, x, x + n){
            if(q.empty()){
                return false;
            }
            if(q.top() < i){
                return false;
            }
            q.pop();
            for(auto x : mp[i - x + 1]){
                q.push(x);
            }
        }
        return true;
    };

    // vector<P> p(n);
    // rep(i, n){
    //     p[i] = {r[i], l[i]};
    // }
    // Sort(p);
    // ll resl = p[0].second, resr = p[0].first;
    // rep(i, 1, n){
    //     auto [pr, pl] = p[i];
    //     chmax(resl, pl - i);
    //     chmin(resr, pr - i);
    // }
    // if(resl > resr){
    //     out(0);
    //     return;
    // }
    
    RandomNumber rnd(mn, mx + 1);
    ll ti = clock();
    ll init = -1;
    map<ll, ll> f;
    while(clock() - ti <= 180 * CLOCKS_PER_SEC / 100){
        ll r = rnd.get();
        if(f[r]) continue;
        if(check(r)){
            init = r;
            break;
        }
    }
    if(init == -1){
        out(0);
        return;
    }

    ll okl = init, okr = init;
    {
        ll ng = 0;
        while(abs(okl - ng) > 1){
            ll mid = (okl + ng) / 2;
            if(check(mid)){
                okl = mid;
            }else{
                ng = mid;
            }
        }
    }
    {
        ll ng = 1e9 + 1;
        while(abs(okr - ng) > 1){
            ll mid = (okr + ng) / 2;
            if(check(mid)){
                okr = mid;
            }else{
                ng = mid;
            }
        }
    }
    out(okr - okl + 1);
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(20);
    
    input();
    solve();
}