#include <bits/stdc++.h>
using namespace std;
const long long INF = 100000000000000000;
int main(){
  int N;
  cin >> N;
  vector<int> A(N * 2);
  for (int i = 0; i < N * 2; i++){
    cin >> A[i];
  }
  vector<long long> L(N + 1);
  L[0] = 0;
  for (int i = 0; i < N; i++){
    L[i + 1] = L[i] + (A[i * 2] - A[i * 2 + 1]);
  }
  vector<long long> R(N + 1);
  R[N] = 0;
  for (int i = N - 1; i >= 0; i--){
    R[i] = R[i + 1] + (A[i * 2 + 1] - A[i * 2]);
  }
  long long ans = -INF;
  for (int i = 0; i <= N; i++){
    ans = max(ans, L[i] + R[i]);
  }
  cout << ans << endl;
}