#include<bits/stdc++.h>
using namespace std;
#define ALL(x) begin(x),end(x)
#define rep(i,n) for(int i=0;i<(n);i++)
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define mod 1000000007
using ll=long long;
const int INF=1000000000;
const ll LINF=1001002003004005006ll;
int dx[]={1,0,-1,0},dy[]={0,1,0,-1};
// ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
template<class T>bool chmax(T &a,const T &b){if(a<b){a=b;return true;}return false;}
template<class T>bool chmin(T &a,const T &b){if(b<a){a=b;return true;}return false;}

struct IOSetup{
    IOSetup(){
        cin.tie(0);
        ios::sync_with_stdio(0);
        cout<<fixed<<setprecision(12);
    }
} iosetup;

template<typename T>
ostream &operator<<(ostream &os,const vector<T>&v){
    for(int i=0;i<(int)v.size();i++) os<<v[i]<<(i+1==(int)v.size()?"":" ");
    return os;
}
template<typename T>
istream &operator>>(istream &is,vector<T>&v){
    for(T &x:v)is>>x;
    return is;
}

signed main(){
    int n,m;cin>>n>>m;

    int me;cin>>me;
    n--;
    vector<int> v(n);
    cin>>v;

    sort(ALL(v));

    if(n+1==m*2){
        cout<<v[0]<<endl;
        return 0;
    }

    auto check=[&](int ban){
        int lim=v[ban]+me+1;
        multiset<int> st;
        rep(i,n)if(i!=ban) st.insert(v[i]);
        rep(_,m){
            int large=*prev(end(st));
            st.erase(prev(end(st)));
            auto ite=st.lower_bound(lim-large);
            if(ite==end(st)) return true;
            st.erase(ite);
        }
        return false;
    };

    int lw=0,hi=n-1,res=-1;
    while(lw<=hi){
        int mid=(lw+hi)/2;
        if(check(mid)) res=mid,hi=mid-1;
        else lw=mid+1;
    }
    if(res<0) cout<<-1<<endl;
    else cout<<v[res]<<endl;
    return 0;
}