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

A = [(v, i) for i, v in enumerate(A, 1)]
A.sort()
pt = 0
pair = []
for i in range(N):
  (a, x), (b, y) = A[i], A[N+i]
  pt += b - a
  pair.append((x, y))

print(pt)
for v in pair:
  print(*v)