#include<bits/stdc++.h>
namespace {
#pragma GCC diagnostic ignored "-Wunused-function"
#include<atcoder/all>
#pragma GCC diagnostic warning "-Wunused-function"
using namespace std;
using namespace atcoder;
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(i,n) for(int i = (int)(n) - 1; i >= 0; i--)
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
template<class T> bool chmax(T& a, const T& b) { if (a < b) { a = b; return true; } else return false; }
template<class T> bool chmin(T& a, const T& b) { if (b < a) { a = b; return true; } else return false; }
using ll = long long;
using P = pair<int,int>;
using VI = vector<int>;
using VVI = vector<VI>;
using VL = vector<ll>;
using VVL = vector<VL>;

} int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  vector<P> lr(n);
  for (auto& [l, r] : lr) {
    cin >> l >> r;
  }
  ranges::sort(lr, {}, [](const auto& x) { return x.second; });
  int imx = 1001001001;
  rep(i, n) chmin(imx, lr[i].second - i);
  ranges::sort(lr, {}, [](const auto& x) { return x.first; });
  int imn = -1001001001;
  rep(i, n) chmax(imn, lr[i].first - i);
  int ans = max(0, imx - imn + 1);
  cout << ans << '\n';
}