N = int(input())
A = list(map(int, input().split()))

T = sorted(range(N * 2), key = lambda i : A[i])
print(sum(A[T[-i - 1]] - A[T[i]] for i in range(N)))
for i in range(N):
	print(T[i] + 1, T[-i - 1] + 1)