N = int(input())
A = list(map(int, input().split()))
As = [(a, i+1) for i, a in enumerate(A)]
As.sort()
ans_li = []
ans = 0
for i in range(1, N+1):
	ans_li.append(f"{As[i-1][1]} {As[N*2-i][1]}")
	ans += As[N*2-i][0] - As[i-1][0]

print(ans)
print(*ans_li, sep="\n")