#include<bits/stdc++.h>
#define REP(i,n) for(int i=0,i##_len=int(n);i<i##_len;++i)
#define rep(i,a,b) for(int i=int(a);i<int(b);++i)
#define All(x) (x).begin(),(x).end()
#define rAll(x) (x).rbegin(),(x).rend()
using namespace std;
using ll = long long;

int main(){
    int N;cin>>N;
    vector<ll> A(2*N);
    REP(i,2*N) cin>>A[i];
    int l=0,r=2*N-1;
    ll ans=0;
    vector<ll> ev(N+1),od(N+1);
    REP(i,N){
        ev[i+1]=ev[i]+A[2*i];
        od[i+1]=od[i]+A[2*i+1];
    }
    REP(i,N+1){
        ans=max(ans,2*ev[i]-2*od[i]+od[N]-ev[N]);
    }
    cout<<ans<<endl;
}