#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
#define rep(i,s,e) for(i64 (i) = (s);(i) < (e);(i)++)
#define all(x) x.begin(),x.end()

template<class T>
static inline std::vector<T> ndvec(size_t&& n, T val) noexcept {
  return std::vector<T>(n, std::forward<T>(val));
}

template<class... Tail>
static inline auto ndvec(size_t&& n, Tail&&... tail) noexcept {
  return std::vector<decltype(ndvec(std::forward<Tail>(tail)...))>(n, ndvec(std::forward<Tail>(tail)...));
}

int main() {
  i64 N;
  cin >> N;
  N *= 2;
  vector<i64> A(N);
  rep(i,0,N) {
    cin >> A[i];
  }
  vector<i64> left(N + 1), right(N + 1);
  rep(i,0,N) {
    if(i % 2 == 0) {
      left[i + 1] = left[i] + A[i];
    }
    else {
      left[i + 1] = left[i] - A[i];
    }
  }
  for(i64 i = N; i --> 0;) {
    if(i % 2 == 1) {
      right[i] = right[i + 1] + A[i];
    }
    else {
      right[i] = right[i + 1] - A[i];
    }
  }
  i64 ans = -1e18;
  for(i64 i = 0;i <= N;i += 2) {
    ans = std::max(ans, left[i] + right[i]);
  }
  cout << ans << endl;
}