/*
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
stO _LHF_ Orz
*/
#include<bits/stdc++.h>
#define pb push_back
#define P make_pair
#define fi first
#define se second
#define rep(i,a,b) for(int i=(a);i<=(b);++i)
#define per(i,a,b) for(int i=(a);i>=(b);--i)
#define bit(s,x) (((s)>>(x))&1)
#define pnp(s) __builtin_popcount(s)
#define lb(s) (s&-s)
using namespace std;
typedef long long ll;
typedef pair<int,int> pii;
typedef vector<int> vi;
inline ll read(){
	ll x=0,f=1,c=getchar();
	while(c<'0'||c>'9')f=(c=='-'?-1:1),c=getchar();
	while(c>='0' && c<='9')x=x*10 + c-'0',c=getchar();
	return x*f;
}
const int N=6e5+3;
const int mod=998244353;
inline void Ad(int &x,int y){x=x+y>=mod?x+y-mod:x+y;}
vector<vi>A,C,AB,CB;
vector<vi>ABC,ACB,ABCB;// can be CBA,CAB,CBAB
int a[N];
vi operator +(vi A,vi B){ for(auto x:B)A.pb(x); return A;}
inline vi top(vector<vi> &A){
	vi ans = A.back();A.pop_back();
	return ans;
}
inline vi del(vi A,int x){ A.erase(A.begin()+x); return A; }
int main(){
	//freopen("data.in","r",stdin);
	//freopen("triples.in","r",stdin);
	//freopen("triples.out","w",stdout);
	int n=read();
	rep(i,1,n){
		int x=a[i]=read();
		if(x==1){
			if(CB.size()) ABC.pb(top(CB)+vi{i});
			else if(ACB.size()){
				vi k=top(ACB);
				int j=a[k[1]]==x;
				A.pb({k[j]});
				ABC.pb(del(k,j)+vi{i});
			}
			else if(ABCB.size()){
				vi k=top(ABCB);
				int j=(a[k[2]]==x)<<1;
				AB.pb({k[j],k[j+1]});
				j^=2;
				ABC.pb({k[j],k[j+1],i});
			}
			else A.pb({i});
		}
		else if(x==3){
			if(AB.size()) ABC.pb(top(AB)+vi{i});
			else if(ACB.size()){
				vi k=top(ACB);
				int j=a[k[1]]==x;
				assert(a[k[j]]==x);
				C.pb({k[j]});
				ABC.pb(del(k,j)+vi{i});
			}
			else if(ABCB.size()){
				vi k=top(ABCB);
				int j=(a[k[2]]==x)<<1;
				CB.pb({k[j],k[j+1]});
				j^=2;
				ABC.pb({k[j],k[j+1],i});
			}
			else C.pb({i});
		}
		else{
			if(A.size()&&C.size()){
				int k1=top(A)[0];
				int k2=top(C)[0];
				if(k1>k2)swap(k1,k2);
				ACB.pb({k1,k2,i});
			}
			else if(A.size())AB.pb(top(A)+vi{i});
			else if(C.size())CB.pb(top(C)+vi{i});
			else if(ABC.size())ABCB.pb(top(ABC)+vi{i});
		}
	}
	printf("%d\n",ABC.size()+ABCB.size());
	for(auto x:ABC){
		int &i=x[0],&j=x[2];
		if(i>j)swap(i,j);
		printf("%d %d %d\n",x[0]-1,x[1]-1,x[2]-1);
		//assert(a[x[1]]==2);
		//assert(((a[x[0]]>a[x[1]])^(a[x[2]]>a[x[1]])));
	}
	for(auto x:ABCB){
		int &i=x[0],&j=x[2];
		if(i>j)swap(i,j);
		printf("%d %d %d\n",x[0]-1,x[1]-1,x[2]-1);
		//assert(a[x[1]]==2);
		//assert((a[x[0]]>a[x[1]])^(a[x[2]]>a[x[1]]));
	}
	return 0;
}