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

xs = [(a, i) for i, a in enumerate(A)]
xs.sort(key=lambda x: x[0])

a = xs[:N]
b = xs[N:]

s = 0
pairs = []
for i in range(N):
    a = xs[i]
    b = xs[-(i+1)]
    s += b[0] - a[0]
    pairs.append((a[1], b[1]))

print(s)
for x, y in pairs:
    print(x+1, y+1)