#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int,int>;
#define rep(i,n) for(int i=0;i<n;i++)

const ll mod = ll(1e9) + 7;
const int INF = 1<<29;

int main(){
    int n;
    cin >> n;
    vector<ll> a(2*n);
    rep(i,2*n) cin >> a[i];
    vector<ll> l,r;
    l.push_back(0l);
    r.push_back(0l);
    for (int i=0;i<2*n;i+=2) l.push_back(l.back() + (a[i]-a[i+1]));
    for (int i=2*n-1;i>=0;i-=2) r.push_back(r.back() + (a[i]-a[i-1]));
    reverse(r.begin(),r.end());
    ll ans = 0l;
    rep(i,l.size()){
        ans = max(ans,l[i]+r[i]);
    }
    cout << ans << endl;
    return 0;
}