//*
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
//*/

#include <bits/stdc++.h>

// #include <atcoder/all>
// #include <atcoder/math>

using namespace std;
// using namespace atcoder;

// #define _GLIBCXX_DEBUG

#define DEBUG(x) cerr << #x << ": " << x << endl;
#define DEBUG_VEC(v)                                        \
    cerr << #v << ":";                                      \
    for (int iiiiiiii = 0; iiiiiiii < v.size(); iiiiiiii++) \
        cerr << " " << v[iiiiiiii];                         \
    cerr << endl;
#define DEBUG_MAT(v)                                \
    cerr << #v << endl;                             \
    for (int iv = 0; iv < v.size(); iv++) {         \
        for (int jv = 0; jv < v[iv].size(); jv++) { \
            cerr << v[iv][jv] << " ";               \
        }                                           \
        cerr << endl;                               \
    }
typedef long long ll;
// #define int ll

#define vi vector<int>
#define vl vector<ll>
#define vii vector<vector<int>>
#define vll vector<vector<ll>>
#define pii pair<int, int>
#define pis pair<int, string>
#define psi pair<string, int>
#define pll pair<ll, ll>
template <class S, class T>
pair<S, T> operator+(const pair<S, T> &s, const pair<S, T> &t) {
    return pair<S, T>(s.first + t.first, s.second + t.second);
}
template <class S, class T>
pair<S, T> operator-(const pair<S, T> &s, const pair<S, T> &t) { return pair<S, T>(s.first - t.first, s.second - t.second); }
template <class S, class T>
ostream &operator<<(ostream &os, pair<S, T> p) {
    os << "(" << p.first << ", " << p.second << ")";
    return os;
}
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define rep1(i, n) for (int i = 1; i <= (int)(n); i++)
#define rrep(i, n) for (int i = (int)(n)-1; i >= 0; i--)
#define rrep1(i, n) for (int i = (int)(n); i > 0; i--)
#define REP(i, a, b) for (int i = a; i < b; i++)
#define in(x, a, b) (a <= x && x < b)
#define all(c) c.begin(), c.end()
void YES(bool t = true) {
    cout << (t ? "YES" : "NO") << endl;
}
void Yes(bool t = true) { cout << (t ? "Yes" : "No") << endl; }
void yes(bool t = true) { cout << (t ? "yes" : "no") << endl; }
void NO(bool t = true) { cout << (t ? "NO" : "YES") << endl; }
void No(bool t = true) { cout << (t ? "No" : "Yes") << endl; }
void no(bool t = true) { cout << (t ? "no" : "yes") << endl; }
template <class T>
bool chmax(T &a, const T &b) {
    if (a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T &a, const T &b) {
    if (a > b) {
        a = b;
        return 1;
    }
    return 0;
}
#define UNIQUE(v) v.erase(std::unique(v.begin(), v.end()), v.end());
const ll inf = 1000000001;
const ll INF = (ll)1e18 + 1;
const long double pi = 3.1415926535897932384626433832795028841971L;
int popcount(ll t) { return __builtin_popcountll(t); }
// int dx[4] = {1, 0, -1, 0}, dy[4] = {0, 1, 0, -1};
// int dx2[8] = { 1,1,0,-1,-1,-1,0,1 }, dy2[8] = { 0,1,1,1,0,-1,-1,-1 };
vi dx = {0, 0, -1, 1}, dy = {-1, 1, 0, 0};
vi dx2 = {1, 1, 0, -1, -1, -1, 0, 1}, dy2 = {0, 1, 1, 1, 0, -1, -1, -1};
struct Setup_io {
    Setup_io() {
        ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
        cout << fixed << setprecision(25);
        cerr << fixed << setprecision(25);
    }
} setup_io;
// constexpr ll MOD = 1000000007;
constexpr ll MOD = 998244353;
// #define mp make_pair
// #define endl '\n'

struct dice {
    mt19937 mt;
    dice() : mt(chrono::steady_clock::now().time_since_epoch().count()) {}
    // [0, x)の一様乱数
    ll operator()(ll x) { return this->operator()(0, x); }
    // [x, y)の一様乱数
    ll operator()(ll x, ll y) {
        uniform_int_distribution<ll> dist(x, y - 1);
        return dist(mt);
    }
    vl operator()(int n, ll x, ll y) {
        vl res(n);
        for (int i = 0; i < n; i++)
            res[i] = this->operator()(x, y);
        return res;
    }
} rnd;

std::random_device seed_gen;
std::mt19937 engine(seed_gen());

ll guchoku(int n, vector<pll> lr) {
    rep(i, n) {
        lr[i].first--;
    }

    sort(all(lr), [](const pll &a, const pll &b) {
        if (a.second != b.second) return a.second < b.second;
        return a.first > b.first;
    });

    ll ans = 0;
    for (ll k = -50; k <= 50; k++) {
        bool ok = true;
        set<int> alive;
        rep(i, n) {
            alive.insert(i + k);
        }

        rep(i, n) {
            auto it = alive.lower_bound(lr[i].first);
            if (it == alive.end() || *it >= lr[i].second) {
                ok = false;
                break;
            }
            alive.erase(it);
        }

        if (ok) {
            ans++;
        }
    }
    return ans;
}

ll solve(int n, vector<pll> lr) {
    vl ls(n), rs(n);
    set<ll> uni;
    rep(i, n) {
        lr[i].first--;
        lr[i].second--;
        ls[i] = lr[i].first;
        rs[i] = lr[i].second;
        if (ls[i] == rs[i]) {
            if (uni.count(ls[i])) {
                return 0;
            }
            uni.insert(ls[i]);
        }
    }

    // ng: k が小さすぎて失敗, ok: セーフ
    sort(all(ls));
    // 全ての p[i] + k が l[i] 以上になれば k が小さすぎたせいではない
    ll ok = -INF;
    rep(i, n) {
        // i + k >= ls[i]
        chmax(ok, ls[i] - i);
    }
    ll ng1 = ok - 1;

    ok = INF;
    sort(all(rs));
    rrep(i, n) {
        // i + k <= rs[i]
        chmin(ok, rs[i] - i);
    }
    ll ng2 = ok + 1;

    // (ng1, ng2) がセーフ
    return max(0LL, ng2 - (ng1 + 1));
}

signed main() {
    int t = 1;
    // cin >> t;
    while (t--) {
        int n = rnd(1, 6);
        cin >> n;
        vector<pll> lr(n);
        rep(i, n) {
            cin >> lr[i].first >> lr[i].second;
            // lr[i].first = rnd(1, 10);
            // lr[i].second = rnd(lr[i].first, 10);
        }
        ll ans = solve(n, lr);
        cout << ans << endl;
        return 0;
        ll gu = guchoku(n, lr);
        DEBUG(gu);
        if (ans != gu) {
            DEBUG(n);
            DEBUG_VEC(lr);
            DEBUG(ans);
            DEBUG(gu);
            assert(ans == gu);
        }
    }
}