N = int(input())
A = list(map(int, input().split()))
people = [(A[i], i) for i in range(2*N)]

people.sort()
ans = 0
pairs = []
for i in range(2*N):
	if i <= 2*N - 1 - i:
		ans += abs(people[i][0] - people[2*N - 1 - i][0])
		pairs.append((people[i][1] + 1, people[2*N - 1 - i][1] + 1))

print(ans)
for p in pairs:
	print(*p)