#include <iostream>
#include <queue>
using namespace std;
using ll = long long;

const int border=60;

int N;
ll H[100010];

bool ok(int k){
    priority_queue<ll> Q;
    for (int i=0;i<N;i++) Q.push(H[i]);
    for (int i=k-1;i>=0;i--){
        if (Q.empty()) break;
        ll enemy = Q.top();
        Q.pop();
        if (i<border && enemy>(1LL<<i)) Q.push(enemy-(1LL<<i));
    }
    return Q.empty();
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin>>N;
    for (int i=0;i<N;i++) cin>>H[i];

    int l=N-1, r=N+border+1;
    while(l+1<r){
        int m = (l+r)/2;
        if(ok(m)) r=m;
        else l=m;
    }

    cout << r << "\n";
    return 0;
}