#include <cstdio>
#include <algorithm>

using namespace std;

const int NMAX = 100001;
int N, ANS;
int v[NMAX], d[NMAX];

int add (int a, int x) {
    if (x == -1) {
        if (a - 1 == 0) {
            return N;
        }
        return a - 1;
    }

    if (x == 1) {
        if (a + 1 == N + 1) {
            return 1;
        }
        return a + 1;
    }

    if (x == -2) {
        a -= 2;
        a %= N;
        if (a == 0) {
            return N;
        }
        if (a == N + 1) {
            return 1;
        }
        return a;
    }
}

inline void complete (int start, int stop) {
    for (int i = start; i <= stop; i++) {
        d[i] = max (d[i - 1], d[i - 3] + v[i - 1] + v[i]);
    }
}

int main () {
    freopen ("oo.in", "r", stdin);
    freopen ("oo.out", "w", stdout);

    scanf ("%d", &N);
    for (int i = 1; i <= N; i++) {
        scanf ("%d", &v[i]);
    }

    if (N == 2) {
        printf ("%d\n", v[1] + v[2]);
        return 0;
    }
    if (N == 3) {
        printf ("%d\n", max (max (v[1] + v[2], v[2] + v[3]), v[1] + v[3]));
        return 0;
    }
    if (N == 4) {
        printf ("%d\n", max (max (v[1] + v[2], v[2] + v[3]), max (v[3] + v[4], v[4] + v[1])));
        return 0;
    }

    d[2] = d[3] = d[4] = v[1] + v[2];
    complete (5, N - 1);
    ANS = d[N - 1];

    d[1] = d[2] = d[3] = v[1] + v[N];
    complete (4, N - 2);
    ANS = max (ANS, d[N - 2]);

    d[0] = d[1] = d[2] = 0;
    complete (3, N);
    ANS = max (ANS, d[N]);

    printf ("%d\n", ANS);

    return 0;
}