import sys, time, random
from collections import deque, Counter, defaultdict
input = lambda: sys.stdin.readline().rstrip()
ii = lambda: int(input())
mi = lambda: map(int, input().split())
li = lambda: list(mi())
inf = 2 ** 63 - 1
mod = 998244353
import itertools
from math import gcd

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

a = li()


ans = inf
it = []
if n == 2:
    ans = f(a[0], a[1])
    it = [(1, 2)]
elif n == 3:
    for v in itertools.permutations(a):
        if ans >= f(f(v[0], v[1]), v[2]):
            one = a.index(v[0])
            a[one] = -1
            two = a.index(v[1])
            a[one] = v[0]
            it = [(one + 1, two + 1), (1, 2)]
            
            ans = min(ans, f(f(v[0], v[1]), v[2]))
else:
    ans = 0
    it = [(1, 2) for _ in range(n - 1)]
print(ans)
for v in it:
    print(*v)