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

def f(x,y):
    if math.gcd(x,y)==1:
        return (x-1)*(y-1)
    return 0
      
if N==2:
    M=f(A[0],A[1])
    print(M)
    print(1,2)
    exit()
    
if N==3:
    ans1=(f(A[2],f(A[0],A[1])),(1,2),(1,2))
    ans2=(f(A[0],f(A[1],A[2])),(2,3),(1,2))
    ans3=(f(A[1],f(A[0],A[2])),(1,3),(1,2))
    ans=min(ans1,ans2,ans3)
    print(ans[0])
    print(*ans[1])
    print(*ans[2])
    exit()
    
print(0)
print(1,2)
print(1,2)
print(N-3,N-2)
for i in range(N-3,1,-1):
    print(1,i)