#include <stdio.h>

int main()
{
   int i, n, X, Y, Z, smax;
	int a[100001];
   FILE *f, *g;
	f=fopen ("oo.in", "r");
	g=fopen ("oo.out", "w");
   fscanf (f, "%d", &n);
   for (i=1; i<=n; i++)
      fscanf (f, "%d ", &a[i]);
   fclose(f);
   smax=0;
   Z = 0;
   X = Y = a[1];
   for (i=2; i<n; i++)
      {
         X=Y;
         if (Z + a[i] > X)
            X = Z + a[i];
         Z = Y; Y=X;
      }
   if (X > smax) smax = X;
   Z=0;
   X=Y=0;
   for (i=2; i<=n; i++)
      {
         X = Y;
         if (X < Z + a[i])
            X = Z + a[i];
         Z = Y; Y = Z;
      }
   if (X>smax) smax=X;
	fprintf(g, "%d\n", smax);
   fclose(g);
   return 0;
}