#include <algorithm>
#include <bitset>
#include <cassert>
#include <chrono>
#include <climits>
#include <cmath>
#include <complex>
#include <cstring>
#include <deque>
#include <functional>
#include <iostream>
#include <iomanip>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <unordered_map>
#include <unordered_set>
#include <vector>
#include <cstdint>
using namespace std;
typedef long long ll;
typedef vector<int> vi;
typedef pair<int,int> pii;
#define MP make_pair
#define PB push_back
#define inf 1000000007
#define rep(i,n) for(int i = 0; i < (int)(n); ++i)
#define all(x) (x).begin(),(x).end()

template<typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val){
    std::fill( (T*)array, (T*)(array+N), val );
}
 
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;
}

int main(){
    int n;
    cin >> n;
    vector<ll> a(2*n);
    rep(i,2*n) cin >> a[i];
    vector<ll> p(n);
    vector<ll> q(n);
    rep(i,n){
        p[i] = a[2*i] - a[2*i+1];
        q[i] = a[2*i+1] - a[2*i];
    }
    rep(i,n-1){
        p[i+1] += p[i];
    }
    for(int i=n-2;i>=0;i--){
        q[i] += q[i+1];
    }
    ll mx = max(p[n-1],q[0]);
    rep(i,n-1){
        chmax(mx,p[i] + q[i+1]);
    }
    cout << mx << endl;
    return 0;
}