#include<cstdio>
#include<cstring>
#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][2];

int rec( int i, bool fl )
{
	if( i == N )
		return 0;

	int &ret = dp[i][fl];
	if( ~ret )
		return ret;

	if( !fl )
		return ret = std::max( rec( i+1, false ), rec( i+1, true )+V[i] );
	else
		return ret = rec( i+1, false );
}

int main()
{
	clr( dp, -1 );

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

	printf( "%d\n", rec( 0, 0 ) );

	return 0;
}