#include <stdio.h>
int p[304];
int a[304];
int get_max(int a, int b) {
return a > b ? a : b;
}
int main() {
freopen("input.txt", "rt", stdin);
int n;
scanf("%d", &n);
for (int i = 1; i <= n; i++) {
scanf("%d", &p[i]);
}
a[1] = p[1];
a[2] = p[1] + p[2];
a[3] = get_max(p[1] + p[3], p[2] + p[3]);
int m = 0;
for (int i = 4; i <= n; i++) {
a[i] = get_max(a[i - 2] + p[i], a[i - 3] + p[i] + p[i - 1]);
}
printf("%d", a[n]);
return 0;
}