#include <cstdio>

#define FOR(i, l, r) for(int i = (l)    ; i <  (r); i++)
#define REV(i, l, r) for(int i = (r) - 1; i >= (l); i--)
#define INC(i, n) FOR(i, 0, n)
#define DEC(i, n) REV(i, 0, n)
#define INC1(i, n) FOR(i, 1, (n) + 1)
#define DEC1(i, n) REV(i, 1, (n) + 1)

typedef long long   signed int LL;
typedef long long unsigned int LU;

template<typename T> inline T max(T a, T b) { return (a > b ? a : b); }

int n, v[1000];
int dp[1000][2];

int main() {
	scanf("%d", &n);
	INC(i, n) { scanf("%d", &v[i]); }
	
	INC(i, n) {
		if(i == 0) {
			dp[0][1] = v[0];
			dp[0][0] = 0;
		} else {
			dp[i][0] =     dp[i - 1][1];
			dp[i][1] = max(dp[i - 1][1], dp[i - 1][0] + v[i]);
		}
	}
	
	printf("%d\n", dp[n - 1][1]);
	
	return 0;
}