#include <bits/stdc++.h>
#define REP(i, n) for(int i = 0;i < n;i++)
#define ll long long
using namespace std;
//typedef vector<unsigned int>vec;
//typedef vector<ll>vec;
//typedef vector<vec> mat;
typedef pair<int, int> P;
typedef pair<ll,ll> LP;
const int dx[8] = {1, 0, -1, 0, 1, -1, -1, 1};
const int dy[8] = {0, 1, 0, -1, 1, 1, -1, -1};
const int INF = 1000000000;
const ll LINF = 1000000000000000000;//1e18
const ll  MOD = 1000000007;
const double PI = acos(-1.0);
const double EPS = 1e-10;

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
//template<class T> inline void add(T &a, T b){a = ((a+b) % MOD + MOD) % MOD;};


int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    int N;
    cin >> N;
    vector<ll> A(2*N);
    REP(i,2*N) cin >> A[i];
    vector<ll> left(N), right(N);
    for(int i=0;i<2*N;i+=2){
        left[i/2] = A[i] - A[i+1];
        right[i/2] = A[i+1] - A[i];
    }
    int l = 0, r = N - 1;
    ll ans = 0;
    ll sum = 0;
    REP(i,N) sum += right[i];
    ans = sum;
    REP(i,N){
        sum -= right[i];
        sum += left[i];
        chmax(ans, sum);
    }
    cout << ans << endl;
}