N = int(input())
A = list(map(int, input().split()))
B = sorted(range(2*N), key=lambda i: A[i])
ans, ans1 = [None]*N, 0

for i in range(N):
    ans[i] = [B[i]+1,B[-1*i-1]+1]
    ans1 += abs(A[ans[i][0]-1]-A[ans[i][1]-1])

print(ans1)

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