#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define sz(x) (int)x.size()
#define ALL(v) v.begin(),v.end()
#define MASK(k) (1LL << (k))
#define BIT(x, i) (((x) >> (i)) & 1)
#define oo (ll)1e18
#define INF (ll)1e9
#define MOD (ll)(1e9 + 7)
using namespace std;
template<class T1, class T2>
bool maximize(T1 &a, T2 b){if(a < b){a = b; return true;} return false;}
template<class T1, class T2>
bool minimize(T1 &a, T2 b){if(a > b){a = b; return true;} return false;}
template<class T1, class T2>
void add(T1 &a, T2 b){a += b; if(a >= MOD) a -= MOD;}
template<class T1, class T2>
void sub(T1 &a, T2 b){a -= b; if(a < 0) a += MOD;}
template<class T>
void cps(T &v){sort(ALL(v)); v.resize(unique(ALL(v)) - v.begin());}
const int MAX = 1e6 + 10;
int N;
pair<int, int> a[MAX];
int ans[MAX];
vector<int> res[MAX];
void solve(){
cin >> N;
for(int i = 1; i <= N; i++){
cin >> a[i].fi;
a[i].se = i;
}
sort(a + 1, a + N + 1);
int cur = 0;
int i = N;
while(i > 0){
if(a[i].fi > i) break;
cur++;
for(int j = 0; j < a[i].fi; j++){
ans[a[i - j].se] = cur;
}
i -= a[i].fi;
}
while(i > 0) ans[a[i--].se] = cur;
for(int i = 1; i <= N; i++) res[ans[i]].push_back(i);
cout << cur << '\n';
for(int i = 1; i <= cur; i++){
cout << sz(res[i]) << ' ';
for(int j: res[i]) cout << j << ' ';
cout << '\n';
}
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
// freopen("capsomayman.inp","r",stdin);
// freopen("capsomayman.out","w",stdout);
int t = 1;
// cin >> t;
while(t--){
solve();
}
return 0;
}
