import sys
input = sys.stdin.readline

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

AI=[(A[i],i+1) for i in range(N*2)]
AI.sort()

ANS=0
L=[]
for i in range(N):
    x,ind1=AI[i]
    y,ind2=AI[N*2-1-i]

    ANS+=abs(x-y)
    L.append((ind1,ind2))

print(ANS)
for x,y in L:
    print(x,y)