#include<bits/stdc++.h>
using namespace std;
#define rep(i,x,y) for (int i=(x);i<=(y);i++)
#define drep(i,y,x) for (int i=(y);i>=(x);i--)
#define pii pair<int,int>
#define fir first
#define sec second
#define MP make_pair
template<typename T> bool chkmin(T &x,T y){return x>y?x=y,1:0;}
template<typename T> bool chkmax(T &x,T y){return x<y?x=y,1:0;}
void file() {
    #ifdef zqj
    freopen("a.in","r",stdin);
    #endif
}
typedef long long ll;
#define sz 666666

int n;
int a[sz];

vector<array<int,3>>ANS;
pii b[sz]; int pos[sz];
int check(int w,int getans=0) {
    rep(i,1,n) pos[i]=0;
    int cc=0;
    rep(i,1,n) if (a[i]!=2) {
        ++cc; b[cc].sec=i; pos[i]=cc;
        if (cc==w) break;
    }
    drep(i,n,1) if (a[i]!=2) {
        b[cc].fir=i; --cc;
        if (!cc) break;
    }
    priority_queue<pii,vector<pii>,greater<pii>>q;
    vector<array<int,3>>V[4][4];
    int res=0;
    rep(i,1,n) {
        if (a[i]==2) {
            while (q.size()&&q.top().fir<i) q.pop();
            if (q.size()) {
                auto [y,x]=q.top(); q.pop();
                V[a[x]][a[y]].push_back({x,i,y});
                ++res;
            }
        }
        else if (pos[i]) q.push(b[pos[i]]);
    }
    if (res!=w) return 0;
    if (!getans) return 1;
    ANS.clear();
    for (auto p:V[1][3]) ANS.push_back(p);
    for (auto p:V[3][1]) ANS.push_back(p);
    rep(t,0,(int)min(V[1][1].size(),V[3][3].size())-1) {
        vector<int>v;
        rep(i,0,2) v.push_back(V[1][1][t][i]),v.push_back(V[3][3][t][i]);
        sort(v.begin(),v.end());
        rep(_x,0,3) rep(_y,_x+1,4) rep(_z,_y+1,5) {
            int x=v[_x],y=v[_y],z=v[_z];
            if (a[x]==2||a[y]!=2||a[z]==2||a[x]==a[z]) continue;
            vector<int>vv;
            rep(i,0,5) if (i!=_x&&i!=_y&&i!=_z) vv.push_back(v[i]);
            if (a[vv[0]]==2||a[vv[1]]!=2||a[vv[2]]==2||a[vv[0]]==a[vv[2]]) continue;
            ANS.push_back({x,y,z});
            ANS.push_back({vv[0],vv[1],vv[2]});
            goto END;
        }
        END:;
    }
    static int vis[sz];
    for (auto [x,y,z]:ANS) vis[x]=vis[y]=vis[z]=1;
    int up=1; if (V[3][3].size()>V[1][1].size()) up=3;
    vector<int>v;
    rep(i,1,n) if (!vis[i]&&a[i]!=2&&a[i]!=up) v.push_back(i);
    rep(t,(int)min(V[1][1].size(),V[3][3].size()),(int)V[up][up].size()-1) {
        auto [x,y,z]=V[up][up][t];
        int w=v.back(); v.pop_back();
        if (w<y) ANS.push_back({w,y,z});
        else ANS.push_back({x,y,w});
    }
    return 1;
}

int main() {
    file();
    cin>>n;
    static int cc[3];
    rep(i,1,n) cin>>a[i];
    std::mt19937 gen(time(0)+(size_t) new char);
    // rep(i,1,n) a[i]=gen()%3+1;
    rep(i,1,n)++cc[a[i]-1];
    int l=0,r=min({cc[0],cc[1],cc[2]}),ans=0;
    while (l<=r) {
        int m=(l+r)>>1;
        if (check(m)) ans=m,l=m+1;
        else r=m-1;
    }
    check(ans,1);
    cout<<ans<<'\n';
    static int vis[sz];
    assert(ans==ANS.size());
    for (auto [x,y,z]:ANS) cout<<x-1<<' '<<y-1<<' '<<z-1<<'\n',assert(a[y]==2&&a[x]!=2&&a[z]!=2&&a[x]!=a[z]&&x<y&&y<z),++vis[x],++vis[y],++vis[z];
    rep(i,1,n) assert(vis[i]<=1);
    return 0;
}