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

newA = []
for i in range(2*N):
	newA.append([A[i],i])

newA.sort()

answer = 0
answer_pair = []

#貪欲していいんですか？
for i in range(N):
	answer += newA[2*N-i-1][0]-newA[i][0]
	answer_pair.append([newA[i][1]+1,newA[2*N-i-1][1]+1])

print(answer)

for i in range(N):
	print(*answer_pair[i])