#include<bits/stdc++.h>
typedef long long ll;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#define ordered_set tree<int, null_type,less_equal<int>, rb_tree_tag,tree_order_statistics_node_update>
#define pb           push_back
#define ff           first
#define ss           second
#define gcd(a, b)    __gcd(a, b)
#define lcm(a, b)    ((a)*((b)/gcd(a,b)))
#define all(v)       v.begin(),v.end()
#define lllim        2147483648
#define Pi           2*acos(0.0)
#define sci(n)	     scanf("%d",&n)
#define scii(n,m)    scanf("%d%d",&n,&m)
#define scl(n)       scanf("%lld",&n)
#define scll(n,m)    scanf("%lld%lld",&n,&m)
#define pii          pair<int,int>
#define pll 	     pair<ll,ll>
#define mem(a,b)     memset(a, b, sizeof(a))
#define fill_(a,b)   fill(a,a+n,b);
#define MOD          1000000007
#define fast_cin     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define filein       freopen("input.txt","r", stdin)
#define watch(x)   	 cerr << __LINE__ << ": " << #x << " = " << (x) << '\n'

/*------------------------------Graph Moves----------------------------*/
//const int fx[]= {+1,-1,+0,+0};
//const int fy[]= {+0,+0,+1,-1};
//const int fx[]= {+0,+0,+1,-1,-1,+1,-1,+1};  // Kings Move
//const int fy[]= {-1,+1,+0,+0,+1,+1,-1,-1}; // Kings Move
//const int fx[]={-2, -2, -1, -1,  1,  1,  2,  2};  // Knights Move
//const int fy[]={-1,  1, -2,  2, -2,  2, -1,  1}; // Knights Move
/*---------------------------------------------------------------------*/

using namespace std;
using namespace __gnu_pbds;
const int maxn=3000005;

vector<ll>pr;
bool mark[maxn];

void si()
{
    for(ll i=4; i<maxn; i+=2) mark[i]=1;
    for(ll i=3; i*i<maxn; i+=2)
        if(!mark[i])
            for(ll j=i*i; j<maxn; j+=i)
                mark[j]=1;
    pr.pb(2);
    for(ll i=3; i<maxn; i+=2)
        if(!mark[i])
            pr.pb(i);
}


int main()
{
    // fast_cin;
    int t,cas=1;
    //si();
    int n;
    scanf("%d",&n);

    int ara[n+2];

    for(int i=0;i<n;i++) scanf("%d",&ara[i]);

    sort(ara,ara+n);

    int mi=ara[n/2-1];
    int mx=ara[n/2];

    int ans=mx-mi;

    printf("%d\n",ans);


    return 0;
}
