#include <bits/stdc++.h>
#define For(i, a, b) for(int (i)=(int)(a); (i)<(int)(b); ++(i))
#define rFor(i, a, b) for(int (i)=(int)(a)-1; (i)>=(int)(b); --(i))
#define rep(i, n) For((i), 0, (n))
#define rrep(i, n) rFor((i), (n), 0)
#define fi first
#define se second
using namespace std;
typedef long long lint;
typedef unsigned long long ulint;
typedef pair<int, int> pii;
typedef pair<int, lint> pil;
typedef pair<lint, int> pli;
typedef pair<lint, lint> pll;
template<class T> bool chmax(T &a, const T &b){if(a<b){a=b; return true;} return false;}
template<class T> bool chmin(T &a, const T &b){if(a>b){a=b; return true;} return false;}
template<class T> T div_floor(T a, T b){
    if(b < 0) a *= -1, b *= -1;
    return a>=0 ? a/b : (a+1)/b-1;
}
template<class T> T div_ceil(T a, T b){
    if(b < 0) a *= -1, b *= -1;
    return a>0 ? (a-1)/b+1 : a/b;
}

constexpr lint mod = 1e9+7;
constexpr lint INF = mod * mod;
constexpr int MAX = 200010;

int main(){
    int n;
    scanf("%d", &n);
    lint a[2*n], L[n+1], R[n+1];
    L[0] = R[0] = 0;
    rep(i, 2*n){
        scanf("%lld", &a[i]);
        if(i % 2 == 0) L[i/2+1] = a[i];
        else R[i/2+1] = a[i];
    }
    partial_sum(L, L+n+1, L);
    partial_sum(R, R+n+1, R);
    lint ans = -INF;
    rep(i, n+1){
        chmax(ans, L[i] + R[n]-R[i]);
    }
    printf("%lld\n", 2*ans - (L[n]+R[n]));
}