#include <bits/stdc++.h>
using namespace std;

#define NDEBUG
#include <cassert>


typedef long long ll;
typedef long double Double;
typedef unsigned long long ull;
typedef pair<int,int> ii;
typedef pair<ll,ll> llll;
typedef pair<double,double> dd;

typedef vector<int> vi;
typedef vector<vector<int>> vvi;
typedef vector<ii> vii;
typedef vector<vector<ii>> vvii;
typedef vector<ll> vll;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<long double> vD;

#define sz(a)  int((a).size())
#define pb  push_back
#define FOR(var,from,to) for(int var=(from);var<=(to);++var)
#define rep(var,n)  for(int var=0;var<(n);++var)
#define rep1(var,n)  for(int var=1;var<=(n);++var)
#define repC2(vari,varj,n)  for(int vari=0;vari<(n)-1;++vari)for(int varj=vari+1;varj<(n);++varj)
#define ALL(c)  (c).begin(),(c).end()
#define RALL(c)  (c).rbegin(),(c).rend()
#define tr(i,c)  for(auto i=(c).begin(); i!=(c).end(); ++i)
#define found(s,e)  ((s).find(e)!=(s).end())
#define mset(arr,val)  memset(arr,val,sizeof(arr))
#define mid(x,y) ((x)+((y)-(x))/2)
#define IN(x,a,b) ((a)<=(x)&&(x)<=(b))
#define cons make_pair



ll gcd(ll a, ll b) { while(a) swap(a, b%=a); return b; }

const ll MOD=1000000007LL;

ll ADD(ll x, ll y) { return (x+y) % MOD; }
ll SUB(ll x, ll y) { return (x-y+MOD) % MOD; }
ll MUL(ll x, ll y) { return x*y % MOD; }
ll POW(ll x, ll e) { ll v=1; for(; e; x=MUL(x,x), e>>=1) if (e&1) v = MUL(v,x); return v; }
ll DIV(ll x, ll y) { /*assert(y%MOD!=0);*/ return MUL(x, POW(y, MOD-2)); }

#define INTSPACE 12
char _buf[INTSPACE*1000000 + 3];

int loadint() {
    if (fgets(_buf, INTSPACE+3, stdin)==NULL) return 0;
    return atoi(_buf);
}

int loadvec(vector<int>& v, int N=-1) {
    if (N == 0) {
        v.clear();
        return 0;
    }
    if (N == -1) {
        N = loadint();
        if (N==0) return 0;
    }
    int bufsize = INTSPACE*N + 3;
    if (fgets(_buf, bufsize, stdin)==NULL) return 0;
    v.resize(N);

    int i=0;
    bool last = false;
    for (char *p=&_buf[0]; ;) {
        char *q = p;
        while (*q > ' ') ++q;
        if (*q == 0x0D || *q == 0x0A) last = true;
        *q = 0;
        v[i++] = atoi(p);
        if (last || i == N) break;
        p = q+1;
    }
    return i;
}
void read_cr() {
    fgets(_buf, 256, stdin);
}


int N;
vi a, aR;
vector<vector<ll>> dp, dpR;


void _build(vi& a, vector<vector<ll>>& dp) {
    dp.assign(N+1, vector<ll>(16, 0));

    vll last(16, LLONG_MAX), curr(16);

    for (int i=N-1; i>=0; --i) {
        curr[0] = a[i]; rep(j,15) curr[j+1] = curr[j] * 4LL;

        rep(j,16) {
            int ix = lower_bound(ALL(last), curr[j]) - last.begin();
            if (ix < 16) {
                dp[i][j] = dp[i+1][ix] + j;
            } else {
                assert(j > 0);
                dp[i][j] = dp[i][j-1] + (N-i);
            }
        }

        swap(last, curr);
    }
}

inline ll solve_neg(int hi) {
    return dpR[N-hi][0]*2 + hi;
}
inline ll solve_pos(int lo) {
    return dp[lo][0]*2;
}


ll solve() {
    vi zeros;

    aR.assign(a.rbegin(), a.rend());
    rep(i,N) {
        if (a[i] == 0) zeros.pb(i);
    }
    int Z = zeros.size();
    if (Z >= 2) {
        rep(i,Z-1) if (zeros[i+1] - zeros[i] >= 2) return -1;
    }

    _build(a, dp);
    _build(aR, dpR);

    if (Z > 0) {
        return solve_neg(zeros[0]) + solve_pos(zeros.back()+1);
    }

    ll best = min(solve_neg(N), solve_pos(0));

    for (int line=1; line<N; ++line) {
        ll neg = solve_neg(line), pos = solve_pos(line);
        best = min(best, neg + pos);
    }

    return best;
}


int main() {
    N = loadvec(a);
    cout << solve() << endl;
    return 0;
}


Measured memory_bytes: 69376