from collections import deque
import math
import sys
input = sys.stdin.readline
N = int(input())
A = list(map(int, input().split()))
ans = []
if N==2:
    g = math.gcd(A[0], A[1])
    ans.append((1, 2))
    if g==1:
        m = (A[0]-1)*(A[1]-1)
    else:
        m = 0
    print(m)
    for i, j in ans:
        print(i, j)
elif N==3:
    g = math.gcd(A[0], A[1])
    if g==1:
        m = (A[0]-1)*(A[1]-1)
    else:
        m = 0
    g = math.gcd(m, A[2])
    if g==1:
        m = (m-1)*(A[2]-1)
    else:
        m = 0

    g = math.gcd(A[0], A[2])
    if g==1:
        m2 = (A[0]-1)*(A[2]-1)
    else:
        m2 = 0
    g = math.gcd(m2, A[1])
    if g==1:
        m2 = (m2-1)*(A[1]-1)
    else:
        m2 = 0

    g = math.gcd(A[1], A[2])
    if g==1:
        m3 = (A[1]-1)*(A[2]-1)
    else:
        m3 = 0
    g = math.gcd(m3, A[0])
    if g==1:
        m3 = (m3-1)*(A[0]-1)
    else:
        m3 = 0

    if m<m2:
        if m<m3:
            print(m)
            print(1, 2)
            print(1, 2)
        else:
            print(m3)
            print(2, 3)
            print(1, 2)
    else:
        if m2<m3:
            print(m2)
            print(1, 3)
            print(1, 2)
        else:
            print(m3)
            print(2, 3)
            print(1, 2)





else:
    A = deque(A)
    while len(A)>1:
        ai = A.popleft()
        aj = A.popleft()
        ans.append((1, 2))
        g = math.gcd(ai, aj)
        if g==1:
            m = (ai-1)*(aj-1)
        else:
            m = 0
        A.append(m)
    print(A[0])
    for i, j in ans:
        print(i, j)