import bisect
import copy
import decimal
import fractions
import heapq
import itertools
import math
import random
import sys
import time
from collections import Counter,deque,defaultdict
from functools import lru_cache,reduce
from heapq import heappush,heappop,heapify,heappushpop,_heappop_max,_heapify_max
def _heappush_max(heap,item):
    heap.append(item)
    heapq._siftdown_max(heap, 0, len(heap)-1)
def _heappushpop_max(heap, item):
    if heap and item < heap[0]:
        item, heap[0] = heap[0], item
        heapq._siftup_max(heap, 0)
    return item
from math import gcd as GCD
read=sys.stdin.read
readline=sys.stdin.readline
readlines=sys.stdin.readlines
write=sys.stdout.write
#import pypyjit
#pypyjit.set_param('max_unroll_recursion=-1')
#sys.set_int_max_str_digits(10**9)

N=int(readline())
A=list(map(int,readline().split()))
def f(a,b):
    if GCD(a,b)>1:
        return 0
    return (a-1)*(b-1)
ans_lst=[]
if N>=4:
    ans=0
    idx0=[i for i in range(N) if A[i]%2==0]
    while len(idx0)<2:
        idx1=[i for i in range(N) if A[i]%2]
        ans_lst.append(idx1[0],idx1[1])
        A=[A[i] for i in range(N) if not i in idx1[:2]]+[(A[idx1[0]]-1)*(A[idx1[1]]-1)]
        N-=1
    ans_lst.append((idx0[0],idx0[1]))
    for i in range(N-2):
        ans_lst.append((0,1))
elif N==3:
    ans=1<<60
    ans_lst=None
    for i,j,k in ((0,1,2),(0,2,1),(1,2,0)):
        a=f(f(A[i],A[j]),A[k])
        if a<ans:
            ans=a
            ans_lst=[(i,j),(0,1)]
elif N==2:
    ans=f(A[0],A[1])
    ans_lst=[(0,1)]
print(ans)
for i,j in ans_lst:
    print(i+1,j+1)