#include <bits/stdc++.h>
using namespace std;
#define FOR(i,m,n) for(int i=(m);i<(n);++i)
#define REP(i,n) FOR(i,0,n)
using ll = long long;
constexpr int INF = 0x3f3f3f3f;
constexpr long long LINF = 0x3f3f3f3f3f3f3f3fLL;
constexpr double EPS = 1e-8;
constexpr int MOD = 998244353;
// constexpr int MOD = 1000000007;
constexpr int DY4[]{1, 0, -1, 0}, DX4[]{0, -1, 0, 1};
constexpr int DY8[]{1, 1, 0, -1, -1, -1, 0, 1};
constexpr int DX8[]{0, -1, -1, -1, 0, 1, 1, 1};
template <typename T, typename U>
inline bool chmax(T& a, U b) { return a < b ? (a = b, true) : false; }
template <typename T, typename U>
inline bool chmin(T& a, U b) { return a > b ? (a = b, true) : false; }
struct IOSetup {
  IOSetup() {
    std::cin.tie(nullptr);
    std::ios_base::sync_with_stdio(false);
    std::cout << fixed << setprecision(20);
  }
} iosetup;

int main() {
  int n; cin >> n;
  vector<pair<int, int>> lr(n); for (auto& [l, r] : lr) cin >> l >> r;
  ranges::sort(lr);
  for (int i = n - 1; i >= 0; --i) {
    lr[i].second -= lr.front().first;
    lr[i].first -= lr.front().first;
  }
  int d = 0;
  REP(i, n) chmax(d, lr[i].first - i);
  for (auto& [l, r] : lr) {
    l = max(0, l - d);
    r -= d;
    if (r < l) {
      cout << 0 << '\n';
      return 0;
    }
  }
  ranges::sort(lr);
  int lb = -1, ub = ranges::min(lr, {}, [](const auto& p) -> int { return p.second; }).second + 1;
  while (ub - lb > 1) {
    const int k = midpoint(lb, ub);
    bool is_valid = true;
    int id = 0;
    priority_queue<int, vector<int>, greater<int>> que;
    REP(i, n) {
      while (id < n && lr[id].first - k <= i) que.emplace(lr[id++].second - k);
      if (que.empty() || que.top() < i) {
        is_valid = false;
        break;
      }
      que.pop();
    }
    (is_valid ? lb : ub) = k;
  }
  cout << lb + 1 << '\n';
  return 0;
}