This submission is migrated from previous version of oj.uz, which used different machine for grading. This submission may have different result if resubmitted.
#include <iostream>
#include <vector>
using namespace std;
using vi = vector<int>;
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	int N;
	cin >> N;
	vi lst[1+N];
	for(int i = 1; i <= N; i++)
	{
		int a;
		cin >> a;
		lst[a].push_back(i);
	}
	vi A(1, 0);
	vi I(1, 0);
	for(int i = N; i >= 1; i--)
	{
		for(int x : lst[i])
		{
			A.push_back(i);
			I.push_back(x);
		}
	}
	vi maxteams(1+N);
	vi sizelim(1+N, 5'000'000);
	vi prev(1+N, 0);
	maxteams[0] = sizelim[0] = 0;
	vi occ[1+N+1];
	if(A[1] + 1 <= N+1)
		occ[A[1] + 1].push_back(1);
	for(int i = A[1]+1; i <= N; i++)
	{
		if(A[i] + i <= N+1)
			occ[A[i] + i].push_back(i);
	}
	for(int i = A[1]; i <= N; i++)
	{
		// cerr << "i = " << i << '\n';
		// if(i < A[1])
		// {
		// 	maxteams[i] = sizelim[i] = prev[i] = -1;
		// 	continue;
		// }
		maxteams[i] = 0;
		for(int j : occ[i+1])
		{
			if(j > i) continue;
			if(maxteams[j-1] != maxteams[i-1]) continue;
			int currsize = max(sizelim[j-1], i-j+1);
			if(maxteams[i] == 0 || sizelim[i] > currsize)
			{
				maxteams[i] = maxteams[i-1] + 1;
				sizelim[i] = currsize;
				prev[i] = j-1;
			}
		}
		// cerr << "phase 1 : " << maxteams[i] << '\n';
		if(maxteams[i] == 0)
		{
			maxteams[i] = maxteams[i-1];
			// for(int j = 1; j <= i; j++) if(A[j] <= i-j+1)
			for(int j : occ[i])
			{
				if(A[j] > i-j+1) continue;
				if(j > i) continue;
				// cerr << i << " <- " << j << ' ' << A[j] << ' ' << i-j+1 << '\n';
				if(maxteams[j-1] != maxteams[i] - 1) continue;
				int currsize = max(sizelim[j-1], i-j+1);
				if(sizelim[i] > currsize)
				{
					sizelim[i] = currsize;
					prev[i] = j-1;
				}
			}
		}
	}
	// for(int i = 1; i <= N; i++) cerr << A[i] << ' ' << I[i] << " : " << maxteams[i] << ' ' << sizelim[i] << ' ' << prev[i] << '\n';
	int ci = N;
	cout << maxteams[N] << '\n';
	for(int z = 1; z <= maxteams[N]; z++)
	{
		// cerr << "ci = " << ci << '\n';
		cout << ci - prev[ci] << ' ';
		for(int q = prev[ci]+1; q <= ci; q++)
			cout << I[q] << ' ';
		cout << '\n';
		ci = prev[ci];
	}
}
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