#include<bits/stdc++.h>
#include<atcoder/all>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
using namespace atcoder;
typedef long long ll;
typedef vector<int> vi;
typedef vector<long long> vl;
typedef vector<vector<int>> vvi;
typedef vector<vector<long long>> vvl;
typedef long double ld;
typedef pair<int, int> P;

ostream& operator<<(ostream& os, const modint& a) {os << a.val(); return os;}
template <int m> ostream& operator<<(ostream& os, const static_modint<m>& a) {os << a.val(); return os;}
template <int m> ostream& operator<<(ostream& os, const dynamic_modint<m>& a) {os << a.val(); return os;}
template<typename T> istream& operator>>(istream& is, vector<T>& v){int n = v.size(); assert(n > 0); rep(i, n) is >> v[i]; return is;}
template<typename U, typename T> ostream& operator<<(ostream& os, const pair<U, T>& p){os << p.first << ' ' << p.second; return os;}
template<typename T> ostream& operator<<(ostream& os, const vector<T>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : " "); return os;}
template<typename T> ostream& operator<<(ostream& os, const vector<vector<T>>& v){int n = v.size(); rep(i, n) os << v[i] << (i == n - 1 ? "\n" : ""); return os;}

template<typename T> void chmin(T& a, T b){a = min(a, b);}
template<typename T> void chmax(T& a, T b){a = max(a, b);}

int main(){
	int n;
	cin >> n;
	vector<P> lr;
	vector<P> rl;
	rep(i, n){
		int l, r;
		cin >> l >> r;
		lr.emplace_back(l, r);
		rl.emplace_back(r, l);
	}
	int mn = 0;
	sort(lr.begin(), lr.end(), [](P left, P right){
		return left < right;
	});
	rep(i, n){
		auto [l, r] = lr[i];
//		cout << l << ' ' << r << "\n";
		chmax(mn, l - (i + 1));
		if(mn + (i + 1) > r){
			cout << "0\n";
			return 0;
		}
	}
	int mx = 1001001001;
	sort(rl.begin(), rl.end(), [](P left, P right){
		return left > right;
	});
	rep(i, n){
		auto [r, l] = rl[i];
//		cout << l << ' ' << r << "\n";
		chmin(mx, r - (n - i));
		if(mx + (n - i) < l){
			cout << "0\n";
			return 0;
		}
	}
//	cout << mn << ' ' << mx << "\n";
	int ans = max(mx - mn + 1, 0);
	cout << ans << "\n";
	return 0;
}