//
// Created by Ngày Được Tự Do on 23/01/2021.
//
#include <bits/stdc++.h>
using namespace std;
pair<int, int> Picktree(int a[], int n) {
if (n == 0) {
return pair<int, int>{0, 1};
}
if (n == 1) {
return pair<int, int>{a[1], 1};
}
if (!Picktree(a, n - 1).second) {
return pair<int, int>{Picktree(a, n - 1).first + a[n], 1};
} else {
if (Picktree(a, n - 1).first > Picktree(a, n - 2).first + a[n]) {
return pair<int, int>{Picktree(a, n - 1).first, 0};
} else {
return pair<int, int>{Picktree(a, n - 2).first + a[n], 1};
}
}
}
int main() {
int n;
cin >> n;
int a[n + 1];
a[0] = 0;
for (int i = 1; i <= n; ++i) {
cin >> a[i];
}
cout << Picktree(a, n).first;
return 0;
}
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