//Man always remember love because of romance only!
#include<bits/stdc++.h>
using namespace std;
#define pa pair<int,int>
#define mp make_pair
#define fi first
#define se second
#define ve vector<int> 
inline int read(){
    int n=0,w=0; char ch=0;
    while(!isdigit(ch)) {w|=ch=='-';ch=getchar();}
    while(isdigit(ch)) n=(n<<3)+(n<<1)+(ch^48),ch=getchar();
    return w?-n:n;
}
inline void write(int x){
	if(x<0) putchar('-'),x=-x;
    if(x>9) write(x/10);
    putchar(x%10+'0');
}
//ABC->CBA,ACB->CAB
//ABCB->CBAB
vector<ve> A,C,AB,CB,ABC;
vector<ve> ACB,ABCB;
//A,C->AB,CB
//AB,CB->ABC->ABCB
//ACB->ABCB,AB+CB 
ve operator +(ve x,ve y){
	for(auto u:y) x.push_back(u);
	return x;
} 
ve top(vector<ve> &x){
	ve res=x.back();
	x.pop_back();
	return res;
} 
ve del(ve x,int k){
	x.erase(x.begin()+k);
	return x;
}
int a[600001];
int main(){
//	freopen(".in","r",stdin);
//	freopen(".out","w",stdout);
	int n=read();
	for(int i=1;i<=n;i++){
		int x=read();
		a[i]=x;
		if(x==1){
			if(CB.size()) ABC.push_back(top(CB)+ve{i});//CB+A->ABC
			else if(ACB.size()){//ACB+A->A+ABC
				ve k=top(ACB);
				int j=a[k[1]]==x;
				A.push_back({k[j]});
				ABC.push_back(del(k,j)+ve{i});
			}else if(ABCB.size()){//ABCB+A->AB+ABC
				ve k=top(ABCB);
				int j=(a[k[2]]==x)<<1;
				AB.push_back({k[j],k[j+1]});
				j^=2;
				ABC.push_back({k[j],k[j+1],i});
			}else A.push_back({i});
		}else if(x==3){
			if(AB.size()) ABC.push_back(top(AB)+ve{i});//AB+C->ABC
			else if(ACB.size()){//ACB+C->C+ABC
				ve k=top(ACB);
				int j=a[k[1]]==x;
				C.push_back({k[j]});
				ABC.push_back(del(k,j)+ve{i});
			}else if(ABCB.size()){//ABCB+C->CB+ABC
				ve k=top(ABCB);
				int j=(a[k[2]]==x)<<1;
				CB.push_back({k[j],k[j+1]});
				j^=2;
				ABC.push_back({k[j],k[j+1],i});
			}else C.push_back({i});
		}else{
			if(A.size()&&C.size()){//A+C+B->ABC	
				int k1=top(A)[0],k2=top(C)[0];
				if(k1>k2) swap(k1,k2);
				ACB.push_back({k1,k2,i});
			}else if(A.size()) AB.push_back(top(A)+ve{i});//A+B->AB
			else if(C.size()) CB.push_back(top(C)+ve{i});//C+B->CB
			else if(ACB.size()){//ABC+B->AB+CB
				ve k=top(ACB);
				int j=a[k[1]]==1;
				AB.push_back({k[j],k[2]});
				CB.push_back({k[j^1],i});
			}else if(ABC.size()) ABCB.push_back(top(ABC)+ve{i});//ABC+B->ABCB
		}
	}
	write(ABC.size()+ABCB.size());
	putchar('\n');
	for(auto x:ABC){
		int &i=x[0],&j=x[2];
		if(i>j) swap(i,j);
		cout<<x[0]-1<<" "<<x[1]-1<<" "<<x[2]-1<<"\n";
	}
	for(auto x:ABCB){
		int &i=x[0],&j=x[2];
		if(i>j) swap(i,j);
		cout<<x[0]-1<<" "<<x[1]-1<<" "<<x[2]-1<<"\n";
	}
	return 0;
}