#include <bits/stdc++.h>
using namespace std;
typedef signed long long ll;

#define _P(...) (void)printf(__VA_ARGS__)
#define FOR(x,to) for(x=0;x<(to);x++)
#define FORR(x,arr) for(auto& x:arr)
#define FORR2(x,y,arr) for(auto& [x,y]:arr)
#define ALL(a) (a.begin()),(a.end())
#define ZERO(a) memset(a,0,sizeof(a))
#define MINUS(a) memset(a,0xff,sizeof(a))
template<class T> bool chmax(T &a, const T &b) { if(a<b){a=b;return 1;}return 0;}
template<class T> bool chmin(T &a, const T &b) { if(a>b){a=b;return 1;}return 0;}
//-------------------------------------------------------

int N;
ll H[101010];

int ok(int v) {
	if(v<N) return 0;
	int CN=N;
	while(v>=60) {
		CN--;
		v--;
		if(CN==0) return 1;
	}
	vector<ll> cand;
	int i;
	FOR(i,CN) cand.push_back(H[i]);
	while(v) {
		v--;
		sort(ALL(cand));
		cand.back()-=1LL<<v;
		if(cand.back()<=0) cand.pop_back();
		else sort(ALL(cand));
		if(cand.empty()) return 1;
	}
	return 0;
}

void solve() {
	int i,j,k,l,r,x,y; string s;
	
	cin>>N;
	FOR(i,N) cin>>H[i];
	sort(H,H+N);
	ll ret=1<<20;
	for(i=19;i>=0;i--) if(ok(ret-(1<<i))) ret-=1<<i;
	cout<<ret<<endl;
}


int main(int argc,char** argv){
	string s;int i;
	if(argc==1) ios::sync_with_stdio(false), cin.tie(0);
	FOR(i,argc-1) s+=argv[i+1],s+='\n'; FOR(i,s.size()) ungetc(s[s.size()-1-i],stdin);
	cout.tie(0); solve(); return 0;
}