#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
const long long MOD = 998244353;
// using mint = modint1000000007;
// const long long MOD = 1000000007;
// using mint = modint;//mint::set_mod(MOD);

#include <bits/stdc++.h>
#define rep(i, a, b) for (ll i = (ll)(a); i < (ll)(b); i++)
#define repeq(i, a, b) for (ll i = (ll)(a); i <= (ll)(b); i++)
#define repreq(i, a, b) for (ll i = (ll)(a); i >= (ll)(b); i--)
#define endl '\n'  // fflush(stdout);
#define cYes cout << "Yes" << endl
#define cNo cout << "No" << endl
#define sortr(v) sort(v, greater<>())
#define pb push_back
#define pob pop_back
#define mp make_pair
#define mt make_tuple
#define FI first
#define SE second
#define ALL(v) (v).begin(), (v).end()
#define INFLL 3000000000000000100LL
#define INF 1000000100
#define PI acos(-1.0L)
#define TAU (PI * 2.0L)

using namespace std;

typedef long long ll;
typedef pair<ll, ll> Pll;
typedef tuple<ll, ll, ll> Tlll;
typedef vector<int> Vi;
typedef vector<Vi> VVi;
typedef vector<ll> Vl;
typedef vector<Vl> VVl;
typedef vector<VVl> VVVl;
typedef vector<Tlll> VTlll;
typedef vector<mint> Vm;
typedef vector<Vm> VVm;
typedef vector<string> Vs;
typedef vector<double> Vd;
typedef vector<char> Vc;
typedef vector<bool> Vb;
typedef vector<Pll> VPll;
typedef priority_queue<ll> PQl;
typedef priority_queue<ll, vector<ll>, greater<ll>> PQlr;

/* inout */
ostream &operator<<(ostream &os, mint const &m) {
    os << m.val();
    return os;
}
istream &operator>>(istream &is, mint &m) {
    long long n;
    is >> n, m = n;
    return is;
}
template <typename T>
ostream &operator<<(ostream &os, const vector<T> &v) {
    int n = v.size();
    rep(i, 0, n) { os << v[i] << " \n"[i == n - 1]; }
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, const vector<vector<T>> &v) {
    int n = v.size();
    rep(i, 0, n) os << v[i];
    return os;
}
template <typename T, typename S>
ostream &operator<<(ostream &os, pair<T, S> const &p) {
    os << p.first << ' ' << p.second;
    return os;
}
template <typename T, typename S>
ostream &operator<<(ostream &os, const map<T, S> &ma) {
    for (auto &[key, val] : ma) {
        os << key << ':' << val << '\n';
    }
    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() ? ' ' : '\n');
        itr++;
    }
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, multiset<T> &st) {
    auto itr = st.begin();
    for (int i = 0; i < (int)st.size(); i++) {
        os << *itr << (i + 1 != (int)st.size() ? ' ' : '\n');
        itr++;
    }
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, queue<T> q) {
    while (q.size()) {
        os << q.front();
        q.pop();
        os << " \n"[q.empty()];
    }
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, deque<T> dq) {
    while (dq.size()) {
        os << dq.front();
        dq.pop_front();
        os << " \n"[dq.empty()];
    }
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, stack<T> st) {
    vector<T> v;
    while (st.size()) {
        v.push_back(st.top());
        st.pop();
    }
    reverse(ALL(v));
    os << v;
    return os;
}
template <class T, class Container, class Compare>
ostream &operator<<(ostream &os, priority_queue<T, Container, Compare> pq) {
    vector<T> v;
    while (pq.size()) {
        v.push_back(pq.top());
        pq.pop();
    }
    os << v;
    return os;
}
template <typename T>
istream &operator>>(istream &is, vector<T> &v) {
    for (T &in : v) is >> in;
    return is;
}
template <typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) {
    is >> p.first >> p.second;
    return is;
}

/* useful */
template <typename T>
int SMALLER(vector<T> &a, T x) {
    return lower_bound(a.begin(), a.end(), x) - a.begin();
}
template <typename T>
int orSMALLER(vector<T> &a, T x) {
    return upper_bound(a.begin(), a.end(), x) - a.begin();
}
template <typename T>
int BIGGER(vector<T> &a, T x) {
    return a.size() - orSMALLER(a, x);
}
template <typename T>
int orBIGGER(vector<T> &a, T x) {
    return a.size() - SMALLER(a, x);
}
template <typename T>
int COUNT(vector<T> &a, T x) {
    return upper_bound(ALL(a), x) - lower_bound(ALL(a), x);
}
template <typename T, typename S>
bool chmax(T &a, S b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <typename T, typename S>
bool chmin(T &a, S b) {
    if (a > b) {
        a = b;
        return 1;
    }
    return 0;
}
template <typename T>
void press(T &v) {
    v.erase(unique(ALL(v)), v.end());
}
template <typename T>
vector<int> zip(vector<T> a) {
    int n = a.size();
    pair<T, int> p[n];
    vector<int> v(n);
    for (int i = 0; i < n; i++) p[i] = make_pair(a[i], i);
    sort(p, p + n);
    int w = 0;
    for (int i = 0; i < n; i++) {
        if (i && p[i].first != p[i - 1].first) w++;
        v[p[i].second] = w;
    }
    return v;
}
template <typename T>
vector<T> vis(vector<T> &v) {
    vector<T> S(v.size() + 1);
    rep(i, 1, S.size()) S[i] += v[i - 1] + S[i - 1];
    return S;
}
template <typename T>
T ceil_div(T a, T b) {
    if (b < 0) a = -a, b = -b;
    return (a >= 0 ? (a + b - 1) / b : a / b);
}
template <typename T>
T floor_div(T a, T b) {
    if (b < 0) a = -a, b = -b;
    return (a >= 0 ? a / b : (a - b + 1) / b);
}
ll dtoll(double d, int g) { return round(d * pow(10, g)); }

const double EPS = 1e-10;

void init() {
    cin.tie(0);
    cout.tie(0);
    ios::sync_with_stdio(0);
    cout.precision(12);
    cout << fixed;
}

// do {} while (next_permutation(ALL(vec)));

/********************************** START **********************************/

void sol2();

int main() {
    init();
    int q = 1;
    // cin >> q;
    while (q--) sol2();
    return 0;
}

/********************************** SOLVE **********************************/

template <typename T>
struct RangeSet {
    set<pair<T, T>> st;
    T TINF;

    RangeSet() {
        TINF = numeric_limits<T>::max() / 2;
        st.emplace(TINF, TINF);
        st.emplace(-TINF, -TINF);
    }
    // [l,r] covered?
    bool covered(T l, T r) {
        assert(l <= r);
        auto ite = prev(st.lower_bound({l + 1, l + 1}));
        return ite->first <= l and r <= ite->second;
    }
    bool covered(T x) { return covered(x, x); }
    // [l, r]がカバーされているなら，その区間を返す.
    // されていないなら[-TINF,-TINF]を返す
    pair<T, T> covered_by(T l, T r) {
        assert(l <= r);
        auto ite = prev(st.lower_bound({l + 1, l + 1}));
        if (ite->first <= l and r <= ite->second) return *ite;
        return make_pair(-TINF, -TINF);
    }
    pair<T, T> covered_by(T x) { return covered_by(x, x); }
    // insert[l,r], 増加量を返す
    T insert(T l, T r) {
        assert(l <= r);
        auto ite = prev(st.lower_bound({l + 1, l + 1}));
        if (ite->first <= l and r <= ite->second) return T(0);
        T sum_erased = T(0);
        if (ite->first <= l and l <= ite->second + 1) {
            l = ite->first;
            sum_erased += ite->second - ite->first + 1;
            ite = st.erase(ite);
        } else
            ite = next(ite);
        while (r > ite->second) {
            sum_erased += ite->second - ite->first + 1;
            ite = st.erase(ite);
        }
        if (ite->first - 1 <= r and r <= ite->second) {
            sum_erased += ite->second - ite->first + 1;
            r = ite->second;
            st.erase(ite);
        }
        st.emplace(l, r);
        return r - l + 1 - sum_erased;
    }
    T insert(T x) { return insert(x, x); }
    // erase [l,r], 減少量を返す
    T erase(T l, T r) {
        assert(l <= r);
        auto ite = prev(st.lower_bound({l + 1, l + 1}));
        if (ite->first <= l and r <= ite->second) {
            // 完全に1つの区間に包含されている
            if (ite->first < l) st.emplace(ite->first, l - 1);
            if (r < ite->second) st.emplace(r + 1, ite->second);
            st.erase(ite);
            return r - l + 1;
        }

        T ret = T(0);
        if (ite->first <= l and l <= ite->second) {
            ret += ite->second - l + 1;  // 消えた
            if (ite->first < l) st.emplace(ite->first, l - 1);
            ite = st.erase(ite);  // 次へ
        } else
            ite = next(ite);
        while (ite->second <= r) {
            ret += ite->second - ite->first + 1;
            ite = st.erase(ite);
        }
        // 右端が区間の間にあるか
        if (ite->first <= r and r <= ite->second) {
            ret += r - ite->first + 1;
            if (r < ite->second) st.emplace(r + 1, ite->second);
            st.erase(ite);
        }
        return ret;
    }
    T erase(T x) { return erase(x, x); }
    // number of range
    int size() { return (int)st.size() - 2; }
    // mex [x,~)
    int mex(T x = 0) {
        auto ite = prev(st.lower_bound({x + 1, x + 1}));
        if (ite->first <= x and x <= ite->second)
            return ite->second + 1;
        else
            return x;
    }
    // mexr (~ , x]
    int mexr(T x = 0) {
        auto ite = prev(st.lower_bound({x + 1, x + 1}));
        if (ite->first <= x and x <= ite->second)
            return ite->first - 1;
        else
            return x;
    }
    void output() {
        cout << "RangeSet : ";
        for (auto &p : st) {
            if (p.first == -TINF or p.second == TINF) continue;
            cout << "[" << p.first << ", " << p.second << "] ";
        }
        cout << "\n";
    }
};

ll sol(int n, vector<ll> l, vector<ll> r) {
    auto check = [&](ll mid) {  // ([...,1,1,1,0,0,0,...])
        vector<pair<ll, ll>> v;
        rep(i, 0, n) v.pb({r[i] + mid, l[i] + mid});
        sort(ALL(v));
        RangeSet<ll> rs;
        vector<ll> ad;
        rep(i, 0, n) {
            ll mx = rs.mex(v[i].SE);
            rs.insert(mx);
            ad.push_back(mx);
        }
        sort(ALL(ad));
        rep(i, 0, n) if (ad[i] > i) return false;
        return true;
    };
    auto binary = [&]() {       // ll
        ll L = -2e9, R = +2e9;  // 解[L,R) 探索範囲(L,R)
        ll mid = L + (R - L) / 2;
        while (R - L > 1) {
            if (check(mid))
                L = mid;
            else
                R = mid;
            mid = L + (R - L) / 2;
        }
        return L;  // L-true R-false
    };
    ll ret = binary();
    return ret;
}

void sol2() {
    int n;
    cin >> n;
    vector<ll> l(n), r(n);
    rep(i, 0, n) cin >> l[i] >> r[i], l[i]--, r[i]--;
    ll li = sol(n, l, r);
    ll maxx = 1e9;
    // rep(i, 0, n) chmax(maxx, r[i]);
    rep(i, 0, n) {
        // l[i] = maxx - l[i];
        // r[i] = maxx - r[i];
        swap(l[i], r[i]);
    }
    ll ri = sol(n, l, r);
    cerr << li << " " << ri << endl;
    ll ans = li - ri;
    cout << ans + 1 << endl;
}