#include <bits/stdc++.h>

using ll   = long long;
using uint = unsigned int;
using ull  = unsigned long long;
using ld   = long double;
template<typename T>
using max_heap = std::priority_queue<T>;
template<typename T>
using min_heap = std::priority_queue<T, std::vector<T>, std::greater<T>>;
constexpr int popcount(const ull v) { return v ? __builtin_popcountll(v) : 0; }
constexpr int log2p1(const ull v) { return v ? 64 - __builtin_clzll(v) : 0; }
constexpr int lsbp1(const ull v) { return __builtin_ffsll(v); }
constexpr int clog(const ull v) { return v ? log2p1(v - 1) : 0; }
constexpr ull ceil2(const ull v) { return 1ULL << clog(v); }
constexpr ull floor2(const ull v) { return v ? (1ULL << (log2p1(v) - 1)) : 0ULL; }
constexpr bool btest(const ull mask, const int ind) { return (mask >> ind) & 1ULL; }
template<typename T> void bset(T& mask, const int ind) { mask |= ((T)1 << ind); }
template<typename T> void breset(T& mask, const int ind) { mask &= ~((T)1 << ind); }
template<typename T> void bflip(T& mask, const int ind) { mask ^= ((T)1 << ind); }
template<typename T> void bset(T& mask, const int ind, const bool b) { (b ? bset(mask, ind) : breset(mask, ind)); }
template<typename T> bool chmin(T& a, const T& b) { return (a > b ? a = b, true : false); }
template<typename T> bool chmax(T& a, const T& b) { return (a < b ? a = b, true : false); }

template<typename T> constexpr T inf_v      = std::numeric_limits<T>::max() / 4;
template<typename Real> constexpr Real pi_v = Real{3.141592653589793238462643383279502884};
constexpr ull TEN(const int n) { return n == 0 ? 1ULL : TEN(n - 1) * 10ULL; }
template<typename F> struct fix : F
{
    fix(F&& f) : F{std::forward<F>(f)} {}
    template<typename... Args> auto operator()(Args&&... args) const { return F::operator()(*this, std::forward<Args>(args)...); }
};
class printer
{
public:
    printer(std::ostream& os_ = std::cout) : os{os_} {}
    template<typename T> int operator()(const T& v) { return os << v, 0; }
    template<typename T> int operator()(const std::vector<T>& vs)
    {
        for (int i = 0; i < (int)vs.size(); i++) { os << (i ? " " : ""), this->operator()(vs[i]); }
        return 0;
    }
    template<typename T> int operator()(const std::vector<std::vector<T>>& vss)
    {
        for (int i = 0; i < (int)vss.size(); i++) { os << (0 <= i or i + 1 < (int)vss.size() ? "\n" : ""), this->operator()(vss[i]); }
        return 0;
    }
    template<typename T, typename... Args> int operator()(const T& v, const Args&... args) { return this->operator()(v), os << ' ', this->operator()(args...), 0; }
    template<typename... Args> int ln(const Args&... args) { return this->operator()(args...), os << '\n', 0; }
    template<typename... Args> int el(const Args&... args) { return this->operator()(args...), os << std::endl, 0; }
    template<typename... Args> int fmt(const std::string& s, const Args&... args) { return rec(s, 0, args...); }

private:
    int rec(const std::string& s, int index) { return os << s.substr(index, s.size()), 0; }
    template<typename T, typename... Args> int rec(const std::string& s, int index, const T& v, const Args&... args) { return index == s.size() ? 0 : s[index] == '%' ? (this->operator()(v), rec(s, index + 1, args...)) : (os << s[index], rec(s, index + 1, v, args...)); }
    std::ostream& os;
};
printer out;

template<typename T, typename F> std::vector<T> generated(const int n, F f)
{
    std::vector<T> ans(n);
    return std::generate(ans.begin(), ans.end(), f), ans;
}
std::vector<int> ioted(const int n, const int offset = 0)
{
    std::vector<int> ans(n);
    return std::iota(ans.begin(), ans.end(), offset), ans;
}
template<typename Vs> Vs reversed(const Vs& vs)
{
    auto ans = vs;
    return std::reverse(ans.begin(), ans.end()), ans;
}
template<typename T, typename F = std::less<T>> std::vector<T> sorted(const std::vector<T>& vs, F comp = F{})
{
    auto ans = vs;
    return std::sort(ans.begin(), ans.end(), comp), ans;
}
template<typename F> std::vector<int> sorted_iota(const int n, F comp = F{}, const int offset = 0) { return sorted(ioted(n, offset), comp); }
class scanner
{
public:
    scanner(std::istream& is_ = std::cin) : is{is_} { is.tie(nullptr), std::ios::sync_with_stdio(false); }
    template<typename T> T val()
    {
        static T v;
        return is >> v, v;
    }
    template<typename T> T val(const T offset) { return val<T>() - offset; }
    template<typename T> std::vector<T> vec(const int n)
    {
        return generated<T>(n, [&] { return val<T>(); });
    }
    template<typename T> std::vector<T> vec(const int n, const T offset)
    {
        return generated<T>(n, [&] { return val<T>(offset); });
    }
    template<typename T> std::vector<std::vector<T>> vvec(const int n0, const int n1)
    {
        return generated<std::vector<T>>(n0, [&] { return vec<T>(n1); });
    }
    template<typename T> std::vector<std::vector<T>> vvec(const int n0, const int n1, const T offset)
    {
        return generated<std::vector<T>>(n0, [&] { return vec<T>(n1, offset); });
    }
    template<typename... Args> auto tup() { return std::tuple<std::decay_t<Args>...>{val<Args>()...}; }
    template<typename... Args> auto tup(const Args&... offsets) { return std::tuple<std::decay_t<Args>...>{val<Args>(offsets)...}; }

private:
    std::istream& is;
};
scanner in;
#    define SHOW(...) static_cast<void>(0)

template<typename T, int n, int i = 0>
auto make_v(int const (&szs)[n], const T x = T{})
{
    if constexpr (i == n) {
        return x;
    } else {
        return std::vector(szs[i], make_v<T, n, i + 1>(szs, x));
    }
}

const auto min_merge    = [](const auto& x1, const auto& x2) { return std::min(x1, x2); };
const auto max_merge    = [](const auto& x1, const auto& x2) { return std::max(x1, x2); };
const auto minmax_merge = [](const auto& x1, const auto& x2) { return decltype(x1){std::min(x1.first, x2.first), std::max(x1.second, x2.second)}; };
const auto sum_merge    = [](const auto& x1, const auto& x2) { return x1 + x2; };
const auto affine_merge = [](const auto& x1, const auto& x2) { return decltype(x1){x1.first * x2.first, x1.first * x2.second + x1.second}; };

const auto plus_comp   = [](const auto& f1, const auto& f2) { return f1 + f2; };
const auto mult_comp   = [](const auto& f1, const auto& f2) { return f1 * f2; };
const auto assign_comp = [](const auto& f1, const auto& f2) { return f1 == inf_v<decltype(f1)> ? f2 : f1; };
const auto affine_comp = [](const auto& f1, const auto& f2) { return decltype(f1){f1.first * f2.first, f1.first * f2.second + f1.second}; };

const auto min_plus_apply      = [](const auto& f, const auto& x, const auto&) { return x + f; };
const auto max_plus_apply      = [](const auto& f, const auto& x, const auto&) { return x + f; };
const auto minmax_plus_apply   = [](const auto& f, const auto& x, const auto&) { return decltype(x){x.first + f, x.second + f}; };
const auto minmax_mult_apply   = [](const auto& f, const auto& x, const auto&) { return f >= 0 ? decltype(x){f * x.first, f * x.second} : decltype(x){f * x.second, f * x.first}; };
const auto min_assign_apply    = [](const auto& f, const auto& x, const auto&) { return f == inf_v<decltype(f)> ? x : f; };
const auto max_assign_apply    = [](const auto& f, const auto& x, const auto&) { return f == inf_v<decltype(f)> ? x : f; };
const auto minmax_assign_apply = [](const auto& f, const auto& x, const auto&) { return f == inf_v<decltype(f)> ? x : decltype(x){f, f}; };
const auto minmax_affine_apply = [](const auto& f, const auto x, const auto&) { return f.first >= 0 ? decltype(x){x.first * f.first + f.second, x.second * f.first + f.second} : decltype(x){x.second * f.first + f.second, x.first * f.first + f.second}; };
const auto sum_plus_apply      = [](const auto& f, const auto& x, const auto& l) { return x + f * l; };
const auto sum_mult_apply      = [](const auto& f, const auto& x, const auto&) { return x * f; };
const auto sum_assign_apply    = [](const auto& f, const auto& x, const auto& l) { return f == inf_v<decltype(f)> ? x : f * l; };
const auto sum_affine_apply    = [](const auto& f, const auto x, const auto& l) { return x * f.first + f.second * l; };

const auto reverse = [](const auto f) { return [f](const auto& x1, const auto& x2) { return f(x2, x1); }; };

template<typename T, typename Merge>
class segtree
{
public:
    segtree(const std::vector<T>& vs, const Merge merge_, const T e_) : size{(int)vs.size()}, half{(int)ceil2(size)}, vals(half << 1, e_), merge{merge_}, e{e_}
    {
        std::copy(vs.begin(), vs.end(), vals.begin() + half);
        for (int i = half - 1; i >= 1; i--) { up(i); }
    }
    T get(const int a) const { return assert(0 <= a and a < size), vals[a + half]; }
    void set(int a, const T& v)
    {
        assert(0 <= a and a < size);
        vals[a += half] = v;
        while (a >>= 1) { up(a); }
    }
    T fold(int l, int r) const
    {
        assert(0 <= l and l <= r and r <= size);
        T accl = e, accr = e;
        for (l += half, r += half; l < r; l >>= 1, r >>= 1) {
            if (l & 1) { accl = merge(accl, vals[l++]); }
            if (r & 1) { accr = merge(vals[--r], accr); }
        }
        return merge(accl, accr);
    }
    template<typename Pred>
    int bs_right(const int l, const Pred& pred) const
    {
        assert(0 <= l and l < size);
        if (not pred(vals[l + half])) { return l + 1; }
        int index      = l + half;
        T acc          = vals[index];
        bool from_left = false;
        while (index >= 1) {
            if (from_left) {
                const T nacc = merge(acc, vals[index << 1 | 1]);
                if (not pred(nacc)) { break; }
                acc = nacc;
            }
            from_left = 1 - (index & 1), index >>= 1;
        }
        if (index == 0) { return size + 1; }
        index = index << 1 | 1;
        while (index < half) {
            index <<= 1;
            const T nacc = merge(acc, vals[index]);
            if (pred(nacc)) { acc = nacc, index |= 1; }
        }
        return index - half + 1;
    }
    template<typename Pred>
    int bs_left(int r, const Pred& pred) const
    {
        assert(0 < r and r <= size);
        r--;
        if (not pred(vals[r + half])) { return r; }
        int index       = r + half;
        T acc           = vals[index];
        bool from_right = false;
        while (index >= 1) {
            if (from_right) {
                const T nacc = merge(vals[index << 1], acc);
                if (not pred(nacc)) { break; }
                acc = nacc;
            }
            from_right = (index & 1), index >>= 1;
        }
        if (index == 0) { return -1; }
        index = index << 1;
        while (index < half) {
            index        = index << 1 | 1;
            const T nacc = merge(vals[index], acc);
            if (pred(nacc)) { acc = nacc, index ^= 1; }
        }
        return index - half;
    }
    friend std::ostream& operator<<(std::ostream& os, const segtree& seg)
    {
        os << "[";
        for (int i = seg.half; i < seg.half + seg.size; i++) { os << seg.vals[i] << (i + 1 == seg.half + seg.size ? "" : ","); }
        return (os << "]\n");
    }

private:
    void up(const int i) { vals[i] = merge(vals[i << 1], vals[i << 1 | 1]); }
    const int size, half;
    std::vector<T> vals;
    const Merge merge;
    const T e;
};
int main()
{
    const auto N  = in.val<int>();
    const auto as = in.vec<ll>(N);
    std::vector<int> lit(N), git(N);
    std::iota(lit.begin(), lit.end(), 0);
    std::sort(lit.begin(), lit.end(), [&](int i, int j) { return as[i] < as[j]; });
    std::iota(git.begin(), git.end(), 0);
    std::sort(git.begin(), git.end(), [&](int i, int j) { return as[i] > as[j]; });
    auto rmq1 = segtree(std::vector<ll>(N, inf_v<ll>), min_merge, inf_v<ll>);
    auto rmq2 = segtree(std::vector<ll>(N, inf_v<ll>), min_merge, inf_v<ll>);
    ll ans    = inf_v<ll>;
    for (const int i : lit) {
        chmin(ans, as[i] + rmq1.fold(0, i) + rmq1.fold(i + 1, N));
        rmq1.set(i, as[i]);
    }
    for (const int i : git) {
        chmin(ans, as[i] + rmq2.fold(0, i) + rmq2.fold(i + 1, N));
        rmq2.set(i, as[i]);
    }
    out.ln(ans == inf_v<ll> ? -1LL : ans);
    return 0;
}