import java.io.;
import java.util.;
import static java.lang.Math.*;
class IPL {
public static void main(String[] args) {
try {
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
int N = Integer.parseInt(br.readLine());
StringTokenizer st = new StringTokenizer(br.readLine());
long arr[] = new long[N];
long dp[] = new long[N];
Arrays.fill(dp,-1);
long _min =Integer.MAX_VALUE;
long tot = 0;
for(int i=0;i<N;i++){
arr[i] = Integer.parseInt(st.nextToken());
tot+=arr[i];
_min = min(_min,arr[i]);
}
if(N<4)
System.out.println(tot-_min);
else{
solve(arr,dp,N-1);
long ans = min(dp[N-1],min(dp[N-2],dp[N-3]));
ans = tot-ans;
System.out.println(ans);
}
} catch (Exception e) {
//TODO: handle exception
}
}
static long solve(long arr[],long dp[],int i){
if(i<3)
return dp[i]=arr[i];
if(dp[i] >-1)
return dp[i];
return dp[i] = min(solve(arr, dp, i-1),min(solve(arr, dp, i-2),solve(arr, dp, i-3))) + arr[i];
}
}