#include <iostream>
#include <vector>

using namespace std;

int main() {

int n;
cin >> n;

vector<int> v(n);
vector<int> s(n, 0);

for (int i=0;i<n;i++) cin >> v[i];

s[0] = v[0];
s[1] = max(v[0], v[1]);

for (int j=2;j<n;j++) {
    s[j] = max(s[j-2] + v[j], s[j-1]);
}

int res=0;

for (int i=0;i<n;i++) {
    res = max(res, s[i]);
}

cout << res << endl;

return 0;
}