#include<bits/stdc++.h>
using namespace std;
typedef vector<int> vi;
vi operator +(vi a,vi b)
{
	for(auto x:b) a.push_back(x);
	return a;
}
vi T(int x)
{
	return vi{x};
}
vi R(vi v)
{
	reverse(v.begin(),v.end());
	return v;
}
void del(vi &a,int w)
{
	a.erase(a.begin()+w);
}
vector<vi> A,C,AB,CB,ABC,ABCB,ACB;
int n;
vi Top(vector<vi> &v)
{
	auto k=v.back();
	v.pop_back();
	return k;
}
bool okok(vi a)
{
	if((a[0]>a[1])==(a[2]>a[1])) return 0;
	return 1;
}
int main()
{
	scanf("%d",&n);
	for(int i=0,x;i<n;i++)
	{
		scanf("%d",&x);
		if(x==1)
		{
			if(CB.size()) ABC.push_back(R(Top(CB)+T(i)));
			else if(ACB.size())
			{
				auto k=Top(ACB);
				A.push_back(T(k[0]));
				del(k,0);
				ABC.push_back(R(k+T(i)));
			}
			else if(ABCB.size()) 
			{
				auto k=Top(ABCB);
				if(k[0]<k[1])
				{
					AB.push_back(T(k[0])+T(k[1]));
					k=T(k[2])+T(k[3]);
				}
				else
				{
					AB.push_back(T(k[0])+T(k[3]));
					k=T(k[2])+T(k[1]);
				}
				ABC.push_back(R(k+T(i)));
			}
			else A.push_back(T(i));
		}
		else if(x==3)
		{
			if(AB.size())
			{
				ABC.push_back(Top(AB)+T(i));
			}
			else if(ACB.size())
			{
				auto k=Top(ACB);
				C.push_back(T(k[1]));
				del(k,1);
				ABC.push_back(k+T(i));
			}
			else if(ABCB.size())
			{
				auto k=Top(ABCB);
				if(k[2]<k[1])
				{
					CB.push_back(T(k[2])+T(k[1]));
					k=T(k[0])+T(k[3]);
				}
				else
				{
					CB.push_back(T(k[2])+T(k[3]));
					k=T(k[0])+T(k[1]);
				}
				ABC.push_back(k+T(i));
			}
			else C.push_back(T(i));
		}
		else
		{
			if(A.size()&&C.size()) ACB.push_back(Top(A)+Top(C)+T(i));
			else if(A.size()) AB.push_back(Top(A)+T(i));
			else if(C.size()) CB.push_back(Top(C)+T(i));
			else if(ACB.size())
			{
				auto k=Top(ACB);
				AB.push_back(T(k[0])+T(k[2]));
				CB.push_back(T(k[1])+T(i));
			}
			else if(ABC.size()) ABCB.push_back(Top(ABC)+T(i));
		}
	}
	for(auto k:ABCB) ABC.push_back(k);
	int ans=ABC.size();
	printf("%d\n",ans);
	for(auto k:ABC)
	{
		if(k[0]>k[2]) swap(k[0],k[2]);
		printf("%d %d %d\n",k[0],k[1],k[2]);
	}
}