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

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

ans=[]
sm=0
for i in range(N):
    l=B[i]
    r=B[2*N-i-1]
    ans.append((l[1]+1,r[1]+1))
    sm+=abs(r[0]-l[0])

print(sm)
for t in ans:
    print(*t)