import sys
from math import gcd
from itertools import permutations
input = sys.stdin.readline

def f(x, y):
    if(gcd(x, y) == 1):
        return (x - 1) * (y - 1)
    return 0


n = int(input())
a = list(map(int, input().split()))

ans = 10 ** 18
ops = []
if(n == 2):
    ans = f(a[0], a[1])
    ops = [(1, 2)]
elif(n == 3):
    ans = f(f(a[0], a[1]), a[2])
    ops = [(1, 2), (1, 2)]
    t = f(f(a[0], a[2]), a[1])
    if(t < ans):
        ans = t
        ops = [(1, 3), (1, 2)]
    t = f(f(a[1], a[2]), a[0])
    if(t < ans):
        ans = t
        ops = [(2, 3), (1, 2)]
else:
    ans = 0
    ops = [(1, 2), (1, 2), (n - 3, n - 2)]
    for i in range(n - 3, 1, -1):
        ops.append((1, i))

print(ans)
for x, y in ops:
    print(x, y)