//* #pragma GCC target("avx2") #pragma GCC optimize("O3") #pragma GCC optimize("unroll-loops") //*/ #include // #include // #include 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 #define vl vector #define vii vector> #define vll vector> #define pii pair #define pis pair #define psi pair #define pll pair template pair operator+(const pair &s, const pair &t) { return pair(s.first + t.first, s.second + t.second); } template pair operator-(const pair &s, const pair &t) { return pair(s.first - t.first, s.second - t.second); } template ostream &operator<<(ostream &os, pair 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 bool chmax(T &a, const T &b) { if (a < b) { a = b; return 1; } return 0; } template 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' void solve() { int n; cin >> n; vector lr(n); vl ls(n), rs(n); rep(i, n) { cin >> lr[i].first >> lr[i].second; lr[i].first--; lr[i].second--; ls[i] = lr[i].first; rs[i] = lr[i].second; } sort(all(lr), [](const pll &a, const pll &b) { if (a.second != b.second) return a.second < b.second; return a.first > b.first; }); // 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; DEBUG(pll(ng1, ng2)); // (ng1, ng2) がセーフ cout << max(0LL, ng2 - (ng1 + 1)) << endl; } signed main() { int t = 1; // cin >> t; while (t--) { solve(); } }