#include <bits/stdc++.h>
using namespace std;

constexpr long long inf = 0x3f3f3f3fLL << 32;

int main() {
  cin.tie(nullptr);
  ios::sync_with_stdio(false);
  int n;
  cin >> n;
  vector<int> a(2 * n);
  for (auto&& e : a) {
    cin >> e;
  }
  long long res = -inf, cur = 0;
  for (int i = 0; i < 2 * n; ++i) {
    if (i & 1) {
      cur += a[i];
    } else {
      cur -= a[i];
    }
  }
  res = cur;
  for (int i = 0; i < 2 * n; i += 2) {
    cur += 2 * a[i];
    cur -= 2 * a[i + 1];
    res = max(res, cur);
  }
  cout << res << '\n';
}