#include<cstdio>
#include<algorithm>
#define rep(i,a) for(int i=0;i<(a);++i)
#define clr(a,v) memset((a),(v),sizeof(a))

const int MAX_N = 1000;

int N, V[MAX_N];
int dp[MAX_N+1][2];

int main()
{
	scanf( "%d", &N );
	rep( i, N )
		scanf( "%d", V+i );

	rep( i, N )
	{
		dp[i+1][0] = std::max( dp[i][0], dp[i][1] );
		dp[i+1][1] = dp[i][0]+V[i];
	}

	printf( "%d\n", std::max( dp[N][0], dp[N][1] ) );

	return 0;
}