#pragma GCC optimize("O3")

#ifdef LOCAL
#include "algo/debug_ver3.hpp"
#else
#define debug(...)
#define debugArr(...)
#endif

#include <bits/stdc++.h>

using namespace std;

int main() {
	cin.tie(nullptr);
	ios::sync_with_stdio(false);

	int n;
	cin >> n;

	vector<int> a(n);
	for (int i = 0; i < n; ++i) {
		cin >> a[i];
	}

	map<int, set<int>> cnt;
	for (int i = 0; i < n; ++i) {
		cnt[a[i]].insert(i);
	}

	vector<int> ans;
	if (count_if(cnt.begin(), cnt.end(), [](pair<const int, set<int>>& p) { return p.second.size() <= 2; })) {
		int l = 0, r = n - 1;
		for (auto [_, st] : cnt) {
			if (st.size() != 2) {
				continue;
			}
			l = max(l, *st.begin());
			r = min(r, *st.rbegin());
		}

		for (int i = l; i < r; ++i) {
			ans.push_back(i);
		}
	}

	cout << ans.size() << '\n';
	for (int i = 0; i < int(ans.size()); ++i) {
		cout << (i == 0 ? "" : " ") << ans[i] + 1;
	}
	cout << '\n';
}