#include <stdio.h>
#define Real(i) ((A[i])+(A[i-1]))
#define maxa(a,b) (((a) > (b)) ? (a) : (b))
#define maxim(a,b,c) (maxa(maxa(a,b),maxa(b,c)))

int i,j,n,m,A[100],B[100],S[100],REZ;

void ReadData(void)
{
 int i;
 freopen("oo.in","r",stdin);
 scanf("%d",&n);
 for (i=1;i<=n;i++)
    {
     scanf("%d",&A[i]);
     B[i]=Real(i);
    }
}

void Emptyy(int S[])
{
 int i;
 for (i=1;i<=n;i++)
    S[i]=0;
}

int DL(int l, int r)
{
 int i,max=0;
 Emptyy(S);
 S[l]=B[l]; S[l+1]=B[l+1]; S[l+2]=B[l+2];
 for (i=l+3;i<=r;i++)
    {
     S[i]=max+B[i];
     if (S[i-3] > max)
       max = S[i-3];
    }
 max=0;
 for (i=l;i<=r;i++)
    if (S[i]>max)
      max=S[i];
 return max;
}

void Solve(void)
{
 int a1,a2,a3;
 a1=DL(3,n-2)+B[1];
 a2=DL(1,n-1);
 a3=DL(2,n);
 REZ=maxim(a1,a2,a3);
}

void PrintData(void)
{
 freopen("oo.out","w",stdout);
 printf("%d\n",REZ);
}

int main()
{
 ReadData();
 Solve();
 PrintData();

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