#ifndef HIDDEN_IN_VS // 折りたたみ用

// 警告の抑制
#define _CRT_SECURE_NO_WARNINGS

// ライブラリの読み込み
#include <bits/stdc++.h>
using namespace std;

// 型名の短縮
using ll = long long; using ull = unsigned long long; // -2^63 ～ 2^63 = 9 * 10^18（int は -2^31 ～ 2^31 = 2 * 10^9）
using pii = pair<int, int>;	using pll = pair<ll, ll>;	using pil = pair<int, ll>;	using pli = pair<ll, int>;
using vi = vector<int>;		using vvi = vector<vi>;		using vvvi = vector<vvi>;	using vvvvi = vector<vvvi>;
using vl = vector<ll>;		using vvl = vector<vl>;		using vvvl = vector<vvl>;	using vvvvl = vector<vvvl>;
using vb = vector<bool>;	using vvb = vector<vb>;		using vvvb = vector<vvb>;
using vc = vector<char>;	using vvc = vector<vc>;		using vvvc = vector<vvc>;
using vd = vector<double>;	using vvd = vector<vd>;		using vvvd = vector<vvd>;
template <class T> using priority_queue_rev = priority_queue<T, vector<T>, greater<T>>;
using Graph = vvi;

// 定数の定義
const double PI = acos(-1);
const vi DX = { 1, 0, -1, 0 }; // 4 近傍（下，右，上，左）
const vi DY = { 0, 1, 0, -1 };
int INF = 1001001001; ll INFL = 4004004003104004004LL; // (int)INFL = 1010931620;

// 入出力高速化
struct fast_io { fast_io() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(18); } } fastIOtmp;

// 汎用マクロの定義
#define all(a) (a).begin(), (a).end()
#define sz(x) ((int)(x).size())
#define lbpos(a, x) (int)distance((a).begin(), std::lower_bound(all(a), x))
#define ubpos(a, x) (int)distance((a).begin(), std::upper_bound(all(a), x))
#define Yes(b) {cout << ((b) ? "Yes\n" : "No\n");}
#define rep(i, n) for(int i = 0, i##_len = int(n); i < i##_len; ++i) // 0 から n-1 まで昇順
#define repi(i, s, t) for(int i = int(s), i##_end = int(t); i <= i##_end; ++i) // s から t まで昇順
#define repir(i, s, t) for(int i = int(s), i##_end = int(t); i >= i##_end; --i) // s から t まで降順
#define repe(v, a) for(const auto& v : (a)) // a の全要素（変更不可能）
#define repea(v, a) for(auto& v : (a)) // a の全要素（変更可能）
#define repb(set, d) for(int set = 0, set##_ub = 1 << int(d); set < set##_ub; ++set) // d ビット全探索（昇順）
#define repis(i, set) for(int i = lsb(set), bset##i = set; i >= 0; bset##i -= 1 << i, i = lsb(bset##i)) // set の全要素（昇順）
#define repp(a) sort(all(a)); for(bool a##_perm = true; a##_perm; a##_perm = next_permutation(all(a))) // a の順列全て（昇順）
#define smod(n, m) ((((n) % (m)) + (m)) % (m)) // 非負mod
#define uniq(a) {sort(all(a)); (a).erase(unique(all(a)), (a).end());} // 重複除去
#define EXIT(a) {cout << (a) << endl; exit(0);} // 強制終了
#define inQ(x, y, u, l, d, r) ((u) <= (x) && (l) <= (y) && (x) < (d) && (y) < (r)) // 半開矩形内判定

// 汎用関数の定義
template <class T> inline ll powi(T n, int k) { ll v = 1; rep(i, k) v *= n; return v; }
template <class T> inline bool chmax(T& M, const T& x) { if (M < x) { M = x; return true; } return false; } // 最大値を更新（更新されたら true を返す）
template <class T> inline bool chmin(T& m, const T& x) { if (m > x) { m = x; return true; } return false; } // 最小値を更新（更新されたら true を返す）
template <class T> inline T get(T set, int i) { return (set >> i) & T(1); }

// 演算子オーバーロード
template <class T, class U> inline istream& operator>>(istream& is, pair<T, U>& p) { is >> p.first >> p.second; return is; }
template <class T> inline istream& operator>>(istream& is, vector<T>& v) { repea(x, v) is >> x; return is; }
template <class T> inline vector<T>& operator--(vector<T>& v) { repea(x, v) --x; return v; }
template <class T> inline vector<T>& operator++(vector<T>& v) { repea(x, v) ++x; return v; }

#endif // 折りたたみ用


#if __has_include(<atcoder/all>)
#include <atcoder/all>
using namespace atcoder;

#ifdef _MSC_VER
#include "localACL.hpp"
#endif

//using mint = modint1000000007;
using mint = modint998244353;
//using mint = modint; // mint::set_mod(m);

namespace atcoder {
	inline istream& operator>>(istream& is, mint& x) { ll x_; is >> x_; x = x_; return is; }
	inline ostream& operator<<(ostream& os, const mint& x) { os << x.val(); return os; }
}
using vm = vector<mint>; using vvm = vector<vm>; using vvvm = vector<vvm>; using vvvvm = vector<vvvm>; using pim = pair<int, mint>;
#endif


#ifdef _MSC_VER // 手元環境（Visual Studio）
#include "local.hpp"
#else // 提出用（gcc）
inline int popcount(int n) { return __builtin_popcount(n); }
inline int popcount(ll n) { return __builtin_popcountll(n); }
inline int lsb(int n) { return n != 0 ? __builtin_ctz(n) : -1; }
inline int lsb(ll n) { return n != 0 ? __builtin_ctzll(n) : -1; }
inline int msb(int n) { return n != 0 ? (31 - __builtin_clz(n)) : -1; }
inline int msb(ll n) { return n != 0 ? (63 - __builtin_clzll(n)) : -1; }
#define dump(...)
#define dumpel(v)
#define dump_list(v)
#define dump_mat(v)
#define input_from_file(f)
#define output_to_file(f)
#define Assert(b) { if (!(b)) while (1) cout << "OLE"; }
#endif


ll naive(int n, vl l, vl r) {
	vi p(n);
	iota(all(p), 0);

	ll res = 0;

	repi(k, -10, 10) {
		bool ok = false;
		repp(p) {
			bool ok2 = true;
			rep(i, n) {
				if (l[i] <= k + p[i] && k + p[i] <= r[i]) {
					;
				}
				else {
					ok2 = false;
					break;
				}
			}

			if (ok2) {
				ok = true;
				break;
			}
		}

		if (ok) res++;
	}

	return res;
}


ll WA(int n, vl l, vl r) {
	vector<pll> lr(n);
	rep(i, n) lr[i] = { l[i], r[i] };
	sort(all(lr));
	rep(i, n) tie(l[i], r[i]) = lr[i];
	dump(l); dump(r);

	ll x_min = -INFL, x_max = INFL;
	rep(i, n) {
		chmax(x_min, l[i] - i);
		chmin(x_max, r[i] - i);
	}
	dump(x_min, x_max);

	if (x_min > x_max) return 0;

	vector<pll> rl(n);
	rep(i, n) rl[i] = { r[i], l[i] };
	sort(all(rl));
	rep(i, n) tie(r[i], l[i]) = rl[i];
	dump(l); dump(r);

	ll y_min = -INFL, y_max = INFL;
	rep(i, n) {
		chmax(y_min, l[i] - i);
		chmin(y_max, r[i] - i);
	}
	dump(y_min, y_max);

	if (y_min > y_max)  return 0;

	return max(y_max - x_min + 1, 0LL);
}


ll solve(int n, vl l, vl r) {
	ll x0 = -1;
	{
		vector<pll> lr(n);
		rep(i, n) lr[i] = { l[i], r[i] };
		sort(all(lr));
		rep(i, n) tie(l[i], r[i]) = lr[i];
		dump(l); dump(r);

		ll x = -INFL;
		rep(i, n) {
			chmax(x, l[i] - i);
		}
		dump(x);

		set<ll, greater<ll>> rem;
		rep(i, n) rem.insert(i);

		repir(i, n - 1, 0) {
			auto it = rem.lower_bound(r[i] - x);
			if (it == rem.end()) return 0;
			ll v = *it;
			if (v < l[i] - x) return 0;
			rem.erase(it);
		}

		x0 = x;
	}

	rep(i, n) l[i] *= -1;
	rep(i, n) r[i] *= -1;
	swap(l, r);

	ll x1 = -1;
	{
		vector<pll> lr(n);
		rep(i, n) lr[i] = { l[i], r[i] };
		sort(all(lr));
		rep(i, n) tie(l[i], r[i]) = lr[i];
		dump(l); dump(r);

		ll x = -INFL;
		rep(i, n) {
			chmax(x, l[i] - i);
		}
		dump(x);

		set<ll, greater<ll>> rem;
		rep(i, n) rem.insert(i);

		repir(i, n - 1, 0) {
			auto it = rem.lower_bound(r[i] - x);
			if (it == rem.end()) return 0;
			ll v = *it;
			if (v < l[i] - x) return 0;
			rem.erase(it);
		}

		x1 = -x - n + 1;
	}

	return max(x1 - x0 + 1, 0LL);
}


void bug_find() {
#ifdef _MSC_VER
	// 合わない入力例を見つける．

	mute_dump = true;

	mt19937_64 mt;
	mt.seed((int)time(NULL));
	uniform_int_distribution<ll> rnd(0LL, 1LL << 60);

	rep(hoge, 100) {
		int n = rnd(mt) % 7 + 1;
		vl l(n), r(n);
		rep(i, n) {
			l[i] = rnd(mt) % 10;
			r[i] = rnd(mt) % 10;
			if (l[i] > r[i]) swap(l[i], r[i]);
		}

		auto res_naive = naive(n, l, r);
		auto res_solve = solve(n, l, r);

		if (res_naive != res_solve) {
			cout << "----------error!----------" << endl;
			cout << "input:" << endl;
			cout << n << endl;
			cout << l << endl;
			cout << r << endl;
			cout << "results:" << endl;
			cout << res_naive << endl;
			cout << res_solve << endl;
			cout << "--------------------------" << endl;
		}
	}

	mute_dump = false;
	exit(0);
#endif
}


int main() {
//	input_from_file("input.txt");
//	output_to_file("output.txt");

	bug_find();

	int n;
	cin >> n;

	vl l(n), r(n);
	rep(i, n) cin >> l[i] >> r[i];

	dump(naive(n, l, r)); dump("----");

	EXIT(solve(n, l, r));
}