#include <bits/stdc++.h>
#define INIT std::ios::sync_with_stdio(false);std::cin.tie(0);
// VAR(int, x);
#define VAR(type, ...)type __VA_ARGS__;Scan(__VA_ARGS__);
template<typename T> void Scan(T& t){std::cin >> t;}
template<typename First,typename...Rest>void Scan(First& first,Rest&...rest){std::cin>>first;Scan(rest...);}
#define OUT(d) std::cout<<(d);
#define FOUT(n, d) std::cout<<std::fixed<<std::setprecision(n)<<(d);
#define SOUT(n, c, d) std::cout<<std::setw(n)<<std::setfill(c)<<(d);
#define SP std::cout<<" ";
#define TAB std::cout<<"\t";
#define BR std::cout<<"\n";
#define ENDL std::cout<<std::endl;
#define FLUSH std::cout<<std::flush;
#define VEC(type, c, n) std::vector<type> c(n);for(auto& i:c)std::cin>>i;
#define MAT(type, c, m, n) std::vector<std::vector<type>> c(m, std::vector<type>(n));for(auto& r:c)for(auto& i:r)std::cin>>i;
#define ALL(a) (a).begin(),(a).end()
#define FOR(i, a, b) for(int i=(a);i<(b);++i)
#define RFOR(i, a, b) for(int i=(b)-1;i>=(a);--i)
#define REP(i, n) for(int i=0;i<int(n);++i)
#define RREP(i, n) for(int i=(n)-1;i>=0;--i)
#define PAIR std::pair<int, int>
#define IN(a0, y, a1, b0, x, b1) (a0<=y && y<a1 && b0<=x && x<b1)
#define SHOW(d) {std::cout << #d << "\t:" << d << "\n";}
#define SHOWVECTOR(v) {std::cout << #v << "\t:";for(const auto& i : v){std::cout << i << " ";}std::cout << "\n";}
#define SHOWVECTOR2(v) {std::cout << #v << "\t:\n";for(const auto& i : v){for(const auto& j : i){std::cout << j << " ";}std::cout << "\n";}}
#define SHOWPAIRVECTOR(v) {for(const auto&& i:v){std::cout<<'('<<i.first<<", "<<i.second<<") ";}std::cout<<"\n";}
#define CHECKTIME(state) {auto start=std::chrono::system_clock::now();state;auto end=std::chrono::system_clock::now();auto res=std::chrono::duration_cast<std::chrono::nanoseconds>(end-start).count();std::cerr<<"[Time:"<<res<<"ns  ("<<res/(1.0e9)<<"s)]\n";}

#define int ll
using ll = long long;
constexpr ll INF = 1LL<<60;

bool isKadomatu(int a, int b, int c){
    return ((a!=b && b!=c && c!=a) && (b==std::max({a, b, c}) || b==std::min({a, b, c})));
}

std::vector<int> can;

bool isWin(int state, int n, bool d){
    REP(i, n){
        if(!(can[i]&state)){
            bool t = isWin(can[i]|state, n, !d);
            if(t){
                return false;
            }
        }
    }
    return true;
}

signed main(){
    INIT;
    CHECKTIME([]()
    {
        VAR(int, n);
        VEC(int, a, n);
        REP(i, n){
            FOR(j, i+1, n){
                FOR(k, j+1, n){
                    if(isKadomatu(a[i], a[j], a[k])){
                        can.push_back((1<<i) + (1<<j) + (1<<k));
                    }
                }
            }
        }
        REP(i, can.size()){
            if(isWin(can[i], can.size(), true)){
                REP(j, n){
                    if(can[i]&(1<<j)){
                        OUT(j)SP;
                    }
                }
                BR;
                return 0;
            }
        }
        OUT(-1)BR;
        return 0;
    }
    ());
    return 0;
}