#include<iostream>
#include<vector>
#include<algorithm>
#include <deque>
using namespace std;
int main(){
int N;
cin >> N;
vector<pair<int,int> > a(N);
for (int i=0;i<N;i++) {
cin >> a[i].first;
a[i].second = i + 1;
}
sort(a.begin(), a.end());
vector<int> teams(N, 0);
vector<int> minmaxteam(N, N);
vector<int> next(N, -1);
vector<int> cumulmax_teams(N, 0);
for (int i=0;i<N;i++){
if (a[i].first > i + 1) teams[i] = 0; else {
if (i - a[i].first < 0) teams[i] = 1; else teams[i] = 1 + cumulmax_teams[i - a[i].first];
}
if (i == 0) cumulmax_teams[i] = teams[i]; else cumulmax_teams[i] = max(teams[i],cumulmax_teams[i - 1]);
}
vector<deque<int> > d(N + 1);
for (int i=0;i<N;i++){
minmaxteam[i] = i + 1;
if (teams[i] > 1) {
deque<int>::iterator e = upper_bound(d[teams[i] - 1].begin(), d[teams[i] - 1].end(), i-a[i].first);
for (deque<int>::iterator it=d[teams[i] - 1].begin(); it != e; it++){
int j = *it;
if (minmaxteam[i] > max(i-j, minmaxteam[j])){
minmaxteam[i] = min(minmaxteam[i], max(i-j, minmaxteam[j]));
next[i] = j;
}
}
}
while (minmaxteam[d[teams[i]].back()] >= minmaxteam[i]) d[teams[i]].pop_back();
d[teams[i]].push_back(i);
}
cout << teams[N - 1] << endl;
int cur = N - 1;
while (cur > -1){
cout << cur - next[cur];
for (int i=next[cur]+1; i<=cur;i++) cout << " " << a[i].second;
cout << endl;
cur = next[cur];
}
return 0;
}
