#include<iostream>
#include<vector>
#include<cassert>
using namespace std;
long long gcd(long long a,long long b)
{
	while(b)
	{
		long long t=a%b;
		a=b;
		b=t;
	}
	return a;
}
long long f(long long x,long long y)
{
	long long g=gcd(x,y);
	if(g>=2)return 0LL;
	x--,y--;
	assert(x==0||y==0||x<=(long long)1e18/y);
	return x*y;
}
vector<pair<int,int> >ans;
long long solve(vector<long long>A)
{
	if(A.size()==1)return A[0];
	int zeroi=-1,onei=-1;
	vector<int>EV,OD;
	for(int i=0;i<A.size();i++)
	{
		if(A[i]==0)zeroi=i;
		else if(A[i]==1)onei=i;
		else
		{
			if(A[i]%2==0)EV.push_back(i);
			else OD.push_back(i);
		}
	}
	if(zeroi!=-1)
	{
		if(zeroi!=A.size()-1)
		{
			ans.push_back(make_pair(zeroi,A.size()-1));
			A.pop_back();
			A.erase(A.begin()+zeroi);
			A.push_back(0);
			return solve(A);
		}
		for(int i=A.size()-1;i--;)
		{
			ans.push_back(make_pair(i,i+1));
		}
		return 0LL;
	}
	if(onei!=-1)
	{
		if(onei!=A.size()-1)
		{
			ans.push_back(make_pair(onei,A.size()-1));
			A.pop_back();
			A.erase(A.begin()+onei);
			A.push_back(0);
			return solve(A);
		}
		for(int i=A.size()-1;i--;)
		{
			ans.push_back(make_pair(i,i+1));
		}
		return 0LL;
	}
	if(EV.size()>=2)
	{
		ans.push_back(make_pair(EV[0],EV[1]));
		A.erase(A.begin()+EV[1]);
		A.erase(A.begin()+EV[0]);
		A.push_back(0);
		return solve(A);
	}
	if(EV.size()==1&&OD.size()>=2||OD.size()>=4)
	{
		long long x=OD[0],y=OD[1];
		ans.push_back(make_pair(OD[0],OD[1]));
		A.push_back(f(A[OD[0]],A[OD[1]]));
		A.erase(A.begin()+OD[1]);
		A.erase(A.begin()+OD[0]);
		return solve(A);
	}
	assert(A.size()<=3);
	if(A.size()==2)
	{
		ans.push_back(make_pair(0,1));
		return f(A[0],A[1]);
	}
	long long x=A[0],y=A[1],z=A[2];
	long long X=f(f(x,y),z),Y=f(f(y,z),x),Z=f(f(z,x),y);
	if(X<=Y&&X<=Z)ans.push_back(make_pair(0,1));
	else if(Y<=X&&Y<=Z)ans.push_back(make_pair(1,2));
	else ans.push_back(make_pair(0,2));
	ans.push_back(make_pair(0,1));
	return min(min(X,Y),Z);
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int N;
	cin>>N;
	vector<long long>A(N);
	for(int i=0;i<N;i++)cin>>A[i];
	cout<<solve(A)<<"\n";
	for(pair<int,int>p:ans)cout<<p.first+1<<" "<<p.second+1<<"\n";
}