#include <string>
#include <vector>

using namespace std;

int asdf;

struct list{
    int time;
    int last;
    int next;
    list() : time(0), last(0), next(0) {}
    list(int c1, int c2, int c3) : time(c1), last(c2), next(c3) {}
};
typedef struct list list;

struct data_{
    int d;
    int less;
    int more;
    int last;
    int next;
    int p;
    int h;
    data_() : d(0), less(0), more(0), last(0), next(0), p(0), h(1) {}
    data_(int c1, int c2, int c3, int c4, int c5, int c6) : d(c1), less(c2), more(c3), last(c4), next(c5), p(c6), h(1) {}
};
typedef struct data_ data_;

//times 데이터 정렬 벡터
vector<data_> time;
int seed;

void UpdateTimeH(int i){
    int lastH=0;
    if(time[i].more!=-1)
        lastH=time[time[i].more].h;
    if(time[i].less!=-1)
        lastH=time[time[i].more].h;
    time[i].h=lastH/2 + lastH%2 +1;
}

void UpdateTimeSpin(int i, int type){//type : 1 -> 반시계 type : 2 -> 시계
    int save_=-1;
    int ii;
    if(type==1){
        ii=time[i].more;
        if(time[ii].less!=-1){
            save_=time[ii].less;
        }
        time[ii].less=i;
        time[i].more=save_;
        UpdateTimeH(i);
        UpdateTimeH(ii);
    }
    
    if(type==2){
        ii=time[i].less;
        if(time[ii].more!=-1){
            save_=time[ii].more;
        }
        time[ii].more=i;
        time[i].less=save_;
        UpdateTimeH(i);
        UpdateTimeH(ii);
    }
    if(time[i].p!=-1 && time[time[i].p].less==i){
        time[time[i].p].less=ii;
    }
    if(time[i].p!=-1 && time[time[i].p].more==i){
        time[time[i].p].more=ii;
    }
    time[ii].p=time[i].p;
    time[i].p=ii;
    if(seed==i) seed=ii;
}

void UpdateTimeE(int i){
    UpdateTimeH(i);
    int ch_=(time[i].less!=-1 ? time[time[i].less].h : 0)-(time[i].more!=-1 ? time[time[i].more].h : 0);
    if(ch_>1)
        UpdateTimeSpin(i, 2);
    if(ch_<-1)
        UpdateTimeSpin(i, 1);
}

void UpdateTime(int num){
    int i = seed;//확인 중인 값
    int ml=0;//1 -> more, 2 -> less
    do{
        if(ml==1) i=time[i].more;
        if(ml==2) i=time[i].less;
        UpdateTimeE(i);
        if(time[i].d > num){
            ml=2;
            if(time[i].less==-1){
                break;
            }
        }
        else{
            ml=1;
            if(time[i].more==-1){
                break;
            }
        }
    }while(time[i].more!=-1 || time[i].less!=-1);//다음 and 이전 값이 있는 경우
    
    int newc=time.size();
    if(ml==1){
        time.push_back({num, -1, -1, i, time[i].next, i});
        time[i].more=newc;
        time[i].next=newc;
        if(time[i].next!=-1) time[time[newc].next].last=newc;
    }else if(ml==2){
        time.push_back({num, -1, -1, time[i].last, i, i});
        time[i].less=newc;
        time[i].last=newc;
        if(time[i].last!=-1) time[time[newc].last].next=newc;
    }
    
    UpdateTimeE(i);
}

long long solution(int n, vector<int> times) {
    if(times.size()==2) return -1;
    asdf=0;
    //데이터 정렬
    time.push_back({times[0], -1, -1, -1, -1, -1});
    for(int i=1, seed=0;i<times.size();i++){
        UpdateTime(times[i]);
    }
    return time[time[time[seed].more].less].less;//time[seed].d*1000000+time[time[seed].more].d*10000+time[time[time[seed].more].more].d*100+time[time[time[time[seed].more].more].more].d;
    return time[0].d*1000000+time[time[0].next].d*10000+time[time[time[0].next].next].d*100+time[time[time[time[0].next].next].next].d;
    long long answer = 0;
    unsigned long long sum=1;
    
    /*list list1;
    
    for(int i=0; i<times.size(); i++){
        sum*=times[i];
    }
    
    int a[100000], newsum;
    
    for(int i=0; i<times.size(); i++){
        a[i]=sum/times[i];
        newsum+=a[i];
    }
    
    if(n>newsum){
        n-=newsum;
    }
    else if(n<newsum){
        
    }
    else if(n==newsum){
        return newsum*(n/times[times.size()-1]);
    }*/
    
    return answer;
}