#include<bits/stdc++.h>
using namespace std;
#define fs first
#define sc second
#define pb push_back
#define mp make_pair
#define eb emplace_back
#define ALL(A) A.begin(),A.end()
#define RALL(A) A.rbegin(),A.rend()
typedef long long LL;
typedef pair<int,int> P;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
template<typename T> T gcd(T a,T b){return b?gcd(b,a%b):a;}
const LL mod=1000000007;
const LL LINF=1LL<<62;
const int INF=1<<30;
int dx[]={1,0,-1,0,1,-1,1,-1};
int dy[]={0,1,0,-1,1,-1,-1,1};



int main(){
    int n;cin >> n;
    vector<LL> a(2*n);
    for (int i = 0; i < 2*n; i++) {
        cin >> a[i];
    }
    vector<LL> l,r;
    for (int i = 0; i < 2*n; i+=2) {
        l.pb(a[i] - a[i+1]);
        r.pb(a[i+1] - a[i]);
    }
    vector<LL> cl(n+1,0),cr(n+1,0);
    for (int i = 0; i < n; i++) {
        cl[i+1] = cl[i] + l[i];
    }
    for (int i = n; i >= 1; i--) {
        cr[i-1] = cr[i] + r[i-1];
    }
    LL ans = -LINF;
    for (int i = 0; i <= n; i++) {
        chmax(ans, cl[i] + cr[i]);
    }
    cout << ans << endl;
    return 0;
}