o18_oct_rock

#include <bits/stdc++.h>

using namespace std;
const int N = 50 + 50 + 10;
int ar[N], dp[N][N];
int n;

int f(int i, int j){
    if(i == j) return ar[i];
    if(i > j) return 0;
    if(dp[i][j] != 0) return dp[i][j];
    int l = 0, r = 0;
    /// choose left hand
    l = ar[i] + max(f(i + 1, j - 1), f(i + 2, j));
    /// choose right hand
    r = ar[j] + max(f(i + 1, j - 1), f(i, j - 2));
    return dp[i][j] = max(l, r);
}

int main(){

    scanf("%d", &n);

    for(int i=1;i<=2*n;i++){
        scanf("%d", &ar[i]);
    }

    printf("%d", f(1, 2*n));

    return 0;
}