#include <stdio.h>
#include <stdlib.h>

int main(void) {
              // your code goes here
              int i, n;
              int maxa, maxb;
              int v[1000]={}, dp[1000]={};

              scanf("%d",&n);

              for(i=0;i<n-1;i++){
                            scanf("%d ",v+i);
              }
              scanf("%d",v+n-1);
              
              dp[0] = v[0];
              dp[1] = v[1]>v[0]?v[1]:v[0];
              
              for(i=2;i<n;i++){
	              maxa=dp[i-2] + v[i];
	              maxb=dp[i-1];
	              dp[i] = maxa>maxb?maxa:maxb;
              }
              
              
              printf("%d\n",dp[n-1]);

              return 0;
}