/*** author: yuji9511 ***/
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using lpair = pair<ll, ll>;
const ll MOD = 1e9+7;
const ll INF = 1e18;
#define rep(i,m,n) for(ll i=(m);i<(n);i++)
#define rrep(i,m,n) for(ll i=(m);i>=(n);i--)
#define printa(x,n) for(ll i=0;i<n;i++){cout<<(x[i])<<" \n"[i==n-1];};
void print() {}
template <class H,class... T>
void print(H&& h, T&&... t){cout<<h<<" \n"[sizeof...(t)==0];print(forward<T>(t)...);}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    ll N;
    ll A[200010];
    cin >> N;
    rep(i,0,2*N) cin >> A[i];
    ll val[200010] = {};
    rep(i,0,N) val[i] = A[2*i] - A[2*i+1];
    ll sum1[100010] = {}, sum2[100010] = {};
    rep(i,0,N) sum1[i+1] = sum1[i] + val[i];
    rep(i,0,N) sum2[i+1] = sum2[i] - val[N-1-i];
    ll ans = -INF;
    rep(i,0,N+1){
        ans = max(ans, sum1[i] + sum2[N-i]);
    }
    print(ans);

    

}