/* ---------- 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;
}