1675B.cpp

#include <bits/stdc++.h> 
using namespace std; 
 
#define fast_io ios::sync_with_stdio(false); cin.tie(nullptr); 
 
int main() { 
    fast_io; 
 
    int t; 
    cin >> t; 
    while (t--) { 
        // solve here 
        long long n;
        cin >> n;

        vector<long long> a(n);
        for (int i = 0 ; i < n; i++) 
            cin >> a[i];

        long long ans = 0;
        for (int i = n - 2; i >= 0; i--){
            while (a[i] >= a[i + 1]){
                ans++;
                a[i] /= 2;

                if (a[i] == 0)
                    break;
            }

            if (a[i] == 0 && a[i + 1] == 0 ){
                ans = -1;
                break;
            }
            
        }

        cout << ans << endl;


    } 
 
    return 0; 
}