#define _USE_MATH_DEFINES
#include <bits/stdc++.h>
using namespace std;
signed main() { 
  ios::sync_with_stdio(false); cin.tie(0);
  //b
  int n;
  cin >> n;
  vector<int> a(n + n);
  for (int i = 0; i < n + n; i++) cin >> a[i];
  vector<long long> left(n + 2), right(n + 2);
  for (int i = 0; i < n; i++) {
    left[i + 1] = a[i * 2] - a[i * 2 + 1];
    right[i + 1] = a[i * 2 + 1] - a[i * 2];
  }
  for (int i = 1; i <= n; i++) left[i] += left[i - 1];
  for (int i = n; i >= 1; i--) right[i] += right[i + 1];
  long long ans = 0;
  for (int i = 1; i <= n; i++) {
    ans = max(ans, left[i] + right[i + 1]);
    ans = max(ans, left[i - 1] + right[i]);
  }
  cout << ans << endl;
  return 0;
}