#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef pair<int,int> P;

int main(){
  int n;
  cin >> n;
  vector<int> a(2*n);
  rep(i,2*n) cin >> a[i];
  vector<ll> l(n,0), r(n,0);
  for (int i = 0; i < 2 * n; i += 2) {
    int x = a[i], y = a[i+1];
    l[i/2] = x - y;
    r[i/2] = y - x;
  }  
  vector<ll> lcum(n+1,0), rcum(n+1,0);
  for (int i = 0; i < n; i++) {
    lcum[i+1] = lcum[i] + l[i];
    rcum[n-i-1] = rcum[n-i] + r[n-i-1];
  }
  ll res = 0;
  for (int i = 0; i <= n; i++) {
    ll sum1 = lcum[i], sum2 = rcum[i];
    res = max(res, sum1 + sum2);
  }
  cout << res << endl;
  return 0;
}