/* ---------- STL Libraries ---------- */ // IO library #include <cstdio> #include <fstream> #include <iomanip> #include <ios> #include <iostream> // algorithm library #include <algorithm> #include <cmath> #include <numeric> #include <random> #include <cstring> #include <cassert> // container library #include <array> #include <bitset> #include <deque> #include <map> #include <unordered_map> #include <queue> #include <set> #include <string> #include <tuple> #include <vector> #include <stack> // type #include <cstdint> /* ---------- Namespace ---------- */ using namespace std; /* ---------- Type ---------- */ using ll = long long; #define int ll #define P pair<ll, ll> /* ---------- Constants */ const double PI = 3.141592653589793238462643383279; const ll MOD = 1e9 + 7; const int INF = 1LL << 55; /* v-v-v-v-v-v-v-v-v Main Part v-v-v-v-v-v-v-v-v */ signed main() { int N; cin >> N; vector<int> A(2 * N); for (int i = 0; i < 2 * N; i++) { cin >> A[i]; } vector<int> B(N); vector<int> S(N+1, 0); for (int i = 0; i < N; i++) B[i] = A[2 * i] - A[2 * i + 1]; for (int i = 0; i< N ;i++) S[i+1] = S[i] + B[i]; int mx = -INF; for (int i = 0; i <= N; i++) mx = max(mx, 2 * S[i] - S[N]); cout << mx << endl; return 0; }