111485

#include <iostream>
#include <vector>
#include <algorithm>
#include <string>
#include <math.h>
#include <climits>

#include <list>
#include <map>
#include <set>
#include <queue>
#include <unordered_map>
#include <unordered_set>
#include <map>
#include <numeric>
#include <functional>

//#include <chrono>
//#include <fstream>
//#include <bits/stdc++.h>

#define mp make_pair
#define pb push_back
#define eb emplace_back
#define x first
#define y second
#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define FOR(i,a,b) for (int i = (a); i < (b); i++)
#define RFOR(i,b,a) for (int i = (b) - 1; i >= (a); i--)

using namespace std;

typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef vector<int> veci;
typedef vector<bool> vecb;
typedef vector<vector<int>> vvi;
typedef vector<vector<bool>> vvb;

const int INF_I = 1e9;
const ll INF_LL = 1e18;

int main() {
    /*ifstream cin("in.txt");
    ofstream cout("out.txt");
    auto start_time = chrono::high_resolution_clock::now();*/

    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);


    int n;
    cin >> n;
    vvb del(n, vecb(n, false));
    vvi last_del(n, veci(n, -1));
    veci a(n);
    for (int i = 0; i < n; i++)
        cin >> a[i];
    for (int i = 0; i < n-1; i++) {
        del[i][i] = true;
        del[i][i + 1] = true;
    }
    del[n - 1][n - 1] = true;

    for (int len = 1; len < n; len++)
        for (int beg = 0; beg < n - len; beg++)
            for (int k = beg + 1; k < beg + len; k++)
                if (del[beg][k] && del[k][beg + len] &&
                    (a[k] > a[beg] && a[k] > a[beg + len] || a[k] < a[beg] && a[k] < a[beg + len])) {
                    last_del[beg][beg + len] = k;
                    del[beg][beg + len] = true;
                    break;
                }

    veci dp(n, 1);
    veci p(n, -1);
    for (int i = 1; i < n; i++) {
        for (int j = 0; j < i; j++) {
            if (dp[j] == 1 && j != 0) {
                continue;
            }
            if (a[i] >= a[j] && dp[j] + 1 > dp[i] && del[j][i] ) {
                dp[i] = dp[j] + 1;
                p[i] = j;
            }
        }
    }

    int cur = n-1;
    if (dp[cur] == 1) {
        cout << "-1\n";
        return 0;
    }
    cout << n - dp[cur] << "\n";

    function<void(int, int)> print = [&](int l, int r) {
        if (l < 0 || r > n || last_del[l][r] == -1)
            return;
        print(l, last_del[l][r]);
        print(last_del[l][r], r);
        cout << last_del[l][r] + 1 << "\n";
    };

    while (cur != -1) {
        print(p[cur], cur);
        cur = p[cur];
    }

    /*auto end_time = chrono::high_resolution_clock::now();
    chrono::duration<double> duration = end_time - start_time;
    cout << duration.count() << "\n";
    cin.close();
    cout.close();*/
    return 0;
}