// Slower C++ solution:
#include<iostream>

#include<algorithm>

#include<string>

#include<vector>

#include<cmath>

#include<map>

#include<iomanip>

#include<queue>

#include<stack>

#include<time.h>

#define rep(i,n)for(ll i=0;i<n;i++)

#define ll long long

#define ggr getchar();getchar();return 0;

#define prique priority_queue

#define inf 1145141919364364

#define double long double

using namespace std;

typedef pair<ll, ll>P;

ll gcd(ll x, ll y) {

	if (y == 0)return x;

	return gcd(y, x % y);

}

ll lcm(ll x, ll y) {

	return x * y / gcd(x, y);

}

ll a[114514];

signed main() {

	ll n, ans = 0;

	cin >> n;

	rep(i, n)cin >> a[i];

	sort(a, a + n);

	for (int i = 0; i <= 114514; i++) {

		if (lower_bound(a, a + n, i) - a == n / 2)ans++;

	}

	if (n % 2 == 1)ans = 0;

	cout << ans << endl;

	ggr

}




// Faster C++ solution for the same problem (measured speedup: 1.74552261461536x):
#include<iostream>

#include<algorithm>

#include<string>

#include<vector>

#include<cmath>

#include<map>

#include<iomanip>

#include<queue>

#include<stack>

#include<time.h>

#define int long long

#define rep(i,n) for(int i=0;i<n;i++)

#define REP(i,n) for(int i=1;i<=n;i++)

#define ggr getchar();getchar();return 0;

#define prique priority_queue

constexpr auto mod = 1000000007;

#define inf 1e15

#define key 1e9

using namespace std;

typedef pair<int, int>P;

template<class T> inline void chmax(T& a, T b) {

	a = std::max(a, b);

}

template<class T> inline void chmin(T& a, T b) {

	a = std::min(a, b);

}

//combination(Nが小さい時はこれを使う)

const int MAX = 330000;

int fac[MAX], finv[MAX], inv[MAX];

void COMinit() {

	fac[0] = fac[1] = 1;

	finv[0] = finv[1] = 1;

	inv[1] = 1;

	for (int i = 2; i < MAX; i++) {

		fac[i] = fac[i - 1] * i % mod;

		inv[i] = mod - inv[mod % i] * (mod / i) % mod;

		finv[i] = finv[i - 1] * inv[i] % mod;

	}

}

int COMB(int n, int k) {

	if (n < k) return 0;

	if (n < 0 || k < 0) return 0;

	return fac[n] * (finv[k] * finv[n - k] % mod) % mod;

}



bool prime(int n) {

	int cnt = 0;

	for (int i = 1; i <= sqrt(n); i++) {

		if (n % i == 0)cnt++;

	}

	if (cnt != 1)return false;

	else return n != 1;

}

int gcd(int x, int y) {

	if (y == 0)return x;

	return gcd(y, x % y);

}

int lcm(int x, int y) {

	return x / gcd(x, y) * y;

}



//繰り返し二乗法（Nが大きい時の場合のcombination)

int mod_pow(int x, int y, int m) {

	int res = 1;

	while (y) {

		if (y & 1) {

			res = res * x % m;

		}

		x = x * x % m;

		y >>= 1;

	}

	return res;

}

int kai(int x, int y) {

	int res = 1;

	for (int i = x - y + 1; i <= x; i++) {

		res *= (i % mod); res %= mod;

	}

	return res;

}

int comb(int x, int y) {

	if (y > x)return 0;

	return kai(x, y) * mod_pow(kai(y, y), mod - 2, mod) % mod;

}

//UnionFind

class UnionFind {

protected:

	int* par, * rank, * size;

public:

	UnionFind(unsigned int size) {

		par = new int[size];

		rank = new int[size];

		this->size = new int[size];

		rep(i, size) {

			par[i] = i;

			rank[i] = 0;

			this->size[i] = 1;

		}

	}

	int find(int n) {

		if (par[n] == n)return n;

		return par[n] = find(par[n]);

	}

	void unite(int n, int m) {

		n = find(n);

		m = find(m);

		if (n == m)return;

		if (rank[n] < rank[m]) {

			par[n] = m;

			size[m] += size[n];

		}

		else {

			par[m] = n;

			size[n] += size[m];

			if (rank[n] == rank[m])rank[n]++;

		}

	}

	bool same(int n, int m) {

		return find(n) == find(m);

	}

	int getsize(int n) {

		return size[find(n)];

	}

};

int dight(int n) {

	int ans = 1;

	while (n >= 10) {

		n /= 10;

		ans++;

	}

	return ans;

}

int dight_sum(int n) {

	int sum = 0;

	rep(i, 20)sum += (n % (int)pow(10, i + 1)) / (pow(10, i));

	return sum;

}

int n;

int a[114514];

signed main() {

	cin >> n;

	rep(i, n)cin >> a[i];

	sort(a, a + n);

	cout << a[n / 2] - a[n / 2 - 1] << endl;

	ggr

}