#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for(int i=0;i<(n);++i)
#define rep1(i, n) for(int i=1;i<=(n);i++)
#define ll long long
using mint = modint998244353;
using P = pair<ll,ll>;
using lb = long double;
using T = tuple<ll, ll, ll>;
#ifdef LOCAL
#  include <debug_print.hpp>
#  define dbg(...) debug_print::multi_print(#__VA_ARGS__, __VA_ARGS__)
#else
#  define dbg(...) (static_cast<void>(0))
#endif

int main()
{
    int n;
    cin >> n;
    vector<int> a(n);
    rep(i,n) cin >> a[i];
    map<int, vector<int>> mp;
    rep(i,n) mp[a[i]].push_back(i);
    int l = 0;
    int r = n-1;
    for(auto p : mp) {
        if(p.second.size()>=3) {
            cout << 0 << endl;
            cout << endl;
            return 0;
        }
        if(p.second.size()<=1) continue;
        l = max(l, p.second[0]);
        r = min(r, p.second[1]);
    }
    if(r-l<0) {
        cout << 0 << endl;
        cout << endl;
        return 0;
    }
    cout << r - l << endl;
    for(int i=l+1;i<=r;i++){
        cout << i << " ";
    }
    cout << endl;
    return 0;
}