#include <algorithm>
#include <iostream>
#include <queue>
#include <utility>
#include <vector>
using namespace std;

#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define REP(i, n) FOR(i,0,n)
template <typename T> bool chmax(T &m, const T q) { return m < q ? (m = q, true) : false; }
template <typename T> bool chmin(T &m, const T q) { return m > q ? (m = q, true) : false; }
template <class T1, class T2> T1 floor_div(T1 num, T2 den) { return (num > 0 ? num / den : -((-num + den - 1) / den)); }

int main() {
    cin.tie(nullptr), ios::sync_with_stdio(false);
    int N;
    cin >> N;
    vector<pair<int, int>> LR(N);
    for (auto &[l, r] : LR) cin >> l >> r;

    sort(LR.begin(), LR.end());

    int all_l_max = -1, all_r_min = 1 << 30;
    for (auto [l, r] : LR) {
        chmax(all_l_max, l);
        chmin(all_r_min, r);
    }

    auto find_feasible = [&]() -> int {
        int now = -1;
        for (auto [L, R] : LR) {
            chmax(now, (int)L - 1);
            ++now;
        }
        return now - (N - 1);
    };

    auto check = [&](int mid) -> bool {
        // [mid, mid + 1, ..., mid + N - 1]
        vector<vector<int>> dp(N);

        for (auto [l, r] : LR) {
            int left = max(l, mid) - mid, right = min(r, mid + N - 1) - mid;
            if (left <= right) dp.at(left).push_back(right);
        }

        priority_queue<int, vector<int>, greater<int>> pq;
        REP(i, N) {
            for (auto r : dp.at(i)) pq.push(r);
            while (pq.size() and pq.top() < i) pq.pop();
            if (pq.empty()) return false;
            pq.pop();
        }

        return true;
    };

    auto binsearch = [&](int ok, int ng) -> int {
        while (abs(ok - ng) > 1) {
            const int mid = floor_div(ok + ng, 2);
            (check(mid) ? ok : ng) = mid;
        }
        return ok;
    };

    const int feasible = find_feasible();

    if (!check(feasible)) {
        puts("0");
    } else {
        int lo = binsearch(feasible, all_l_max - N);
        int hi = binsearch(feasible, all_r_min + 1);

        cout << abs(hi - lo) + 1 << '\n';
    }
}