#include <bits/stdc++.h>
using namespace std;
int n,a[200005],b[200005],cnt1,cnt2,cnt3,x,y,ans,l[200005],u[200005],v[200005];
int main() {
    //freopen("candy1.in","r",stdin);
    //freopen("candy1.out","w",stdout);
    cin>>n;
    for(int i=1;i<=n;i++){
    	cin>>a[i];
    	b[i]=a[i]%3;
	}
	for(int i=1;i<=n;i++){
		if(b[i]==0){
			cnt1++;
			l[cnt1]=i;
		}
		if(b[i]==1){
			cnt2++;
			u[cnt2]=i;
		}
		if(b[i]==2){
			cnt3++;
			v[cnt3]=i;
		}
	}
	if(cnt3<=cnt2&&cnt3<=cnt1){
		ans=cnt3;
		x=(cnt2-cnt3)/3;
		y=(cnt1-cnt3)/3;
		ans+=x+y;
		cout<<ans<<endl;
		for(int i=1;i<=cnt3;i++){
			cout<<l[i]<<' '<<u[i]<<' '<<v[i]<<endl;
		}
		if(x>0){
			for(int i=cnt3+1;i+2<=cnt2;i+=3){
				cout<<u[i]<<' '<<u[i+1]<<' '<<u[i+2]<<endl;
			}
		}
		if(y>0){
			for(int i=cnt3+1;i+2<=cnt1;i+=3){
				cout<<l[i]<<' '<<l[i+1]<<' '<<l[i+2]<<endl;
			}
		}
	}else if(cnt2<=cnt3&&cnt2<=cnt1){
		ans=cnt2;
		x=(cnt3-cnt2)/3;
		y=(cnt1-cnt2)/3;
		ans+=x+y;
		cout<<ans<<endl;
		for(int i=1;i<=cnt2;i++){
			cout<<l[i]<<' '<<u[i]<<' '<<v[i]<<endl;
		}
		if(x>0){
			for(int i=cnt2+1;i+2<=cnt3;i+=3){
				cout<<v[i]<<' '<<v[i+1]<<' '<<v[i+2]<<endl;
			}
		}
		if(y>0){
			for(int i=cnt2+1;i+2<=cnt1;i+=3){
				cout<<l[i]<<' '<<l[i+1]<<' '<<l[i+2]<<endl;
			}
		}
	}else if(cnt1<=cnt2&&cnt1<=cnt3){
		ans=cnt1;
		x=(cnt2-cnt1)/3;
		y=(cnt3-cnt1)/3;
		ans+=x+y;
		cout<<ans<<endl;
		for(int i=1;i<=cnt1;i++){
			cout<<l[i]<<' '<<u[i]<<' '<<v[i]<<endl;
		}
		if(x>0){
			for(int i=cnt1+1;i+2<=cnt2;i+=3){
				cout<<u[i]<<' '<<u[i+1]<<' '<<u[i+2]<<endl;
			}
		}
		if(y>0){
			for(int i=cnt1+1;i+2<=cnt3;i+=3){
				cout<<v[i]<<' '<<v[i+1]<<' '<<v[i+2]<<endl;
			}
		}
	}
    return 0;
}

竟然是撒死给！