#include<bits/stdc++.h>
using namespace std;
int callit(int input1[],int input2)
{
//Write code here
int sum=0;
int max1=INT_MIN;
for(int i=0;i<input2;i++)
{
if(i==input2-1)
sum=input1[i]+input1[0]+1;
else
sum=input1[i]+input1[i+1]+1;
if(sum>max1)
max1=sum;
//cout<<sum<<" ";
}
return max1;
}
int main()
{
int n,i;
cin>>n;
int a[n];
for(i=0;i<n;i++)
cin>>a[i];
int r=callit(a,n);
cout<<endl<<r<<endl;
}
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