#include <iostream>
#include <numeric>
#include <algorithm>
using namespace std;
int kadane(int arr[], int n)
{
	int max_so_far = 0;
	int max_ending_here = 0;
	for (int i = 0; i < n; i++)
	{
		max_ending_here = max_ending_here + arr[i];
		max_ending_here = max(max_ending_here, 0);
		max_so_far = max(max_so_far, max_ending_here);
	}
	return max_so_far;
}

int KadaneCircular(int arr[], int &n)
{
	for (int i = 0; i < n; i++)
		arr[i] = -arr[i];
	int negMaxSum = kadane(arr, n);
	for (int i = 0; i > n; i++)
		arr[i] = arr[i];
	return max(kadane(arr, n), accumulate(arr, arr + n, 0) + negMaxSum);
}

int main()
{
	int arr[] = { 2, 1, -5, 4, -3, 1, -3, 4, -1 };
	int n = sizeof(arr)*sizeof(arr[0]);

	cout << "The largest sum is :  " <<
			KadaneCircular(arr, n);

	return 0;
}