#include<cstdio>
#include<cstdlib>
#include<ctime>
#include<algorithm>
using namespace std;
const int max_n = 100010;
int A[max_n], n;
int randPartition(int A[], int left, int right) {
	int p = round(1.0*rand() / RAND_MAX*(right - left)) + left;
	swap(A[p], A[left]);
	int temp = A[left];
	while(left<right){
		while (left < right&&A[right] > temp)right--;
		A[left] = A[right];
		while (left < right&&A[left] <= temp)left++;
		A[right] = A[left];
	}
	A[left] = temp;
	return left;
}
void randSelect(int A[], int left, int right, int K) {
	if (left == right)return;
	int p = randPartition(A, left, right);
	int M = p - left + 1;
	if (K == M)return;
	if (K < M) {
		randSelect(A, left, p - 1, K);
	}
	else {
		randSelect(A, p + 1, right, K - M);
	}
}
int main() {
	srand((unsigned)time(NULL));
	int sum = 0, sum1 = 0;
	scanf("%d", &n);
	for (int i = 0; i < n; i++) {
		scanf("%d", &A[i]);
		sum += A[i];
	}
	randSelect(A, 0, n - 1, n / 2);
	for (int i = 0; i < n / 2; i++) {
		sum1 += A[i];
	}
	printf("%d\n", (sum - sum1) - sum1);
	return 0;
}