#include <stdio.h>

int main() {
    int N;
    int V[1000];
    
    scanf("%d", &N);
    
    int i;
    for (int i=0; i<N; i++) {
        scanf("%d", &(V[i]));
    }
    
    if (N == 1)
        return V[0];
    
    if (N == 2) {
        if (V[0] > V[1])
            return V[0];
        else
            return V[1];
    }
    
    int s1, s2;
    s1 = takeSushi(0, 0, N, V);
    s2 = takeSushi(0, 1, N, V);
    if (s1 > s2)
        return s1;
    else
        return s2;
}

int takeSushi(int score, int position, int N, int V[]) {
    score += V[position];
    
    if (position == N-1 || position == N-2) {
        return score;
    }
    
    if (position == N-3) {
        return score + V[N-1];
    }
    
    int s1, s2;
    s1 = takeSushi(score, position+2, N, V);
    s2 = takeSushi(score, position+3, N, V);
    
    if (s1 > s2)
        return s1;
    else
        return s2;
}