2<=N<=10^5 ;
2<=K<=N ;
0<=integer in N<=10^9 ;

#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
#include <limits.h>

#define MAX 100000
#define MAX_VAL 1000000001

int list[MAX];

int main() {

    int N, K;
    int i;
    int unfairness=0;
    scanf_s("%d %d", &N, &K);
    int set = K - 1;
    for (i = 0; i < N; i++)
        scanf_s("%d", &list[i]);
    for (int l = 0; l < N - 1; l++){
        for (int j = 0; j < N - l - 1; j++)
        {
            if (list[j] > list[j + 1])
            {
                int temp;
                temp = list[j];
                list[j] = list[j + 1];
                list[j + 1] = temp;
            }
        }
    }
    for (int x = 0; x < N - set; x++)
    {
        int differ = list[x + set] - list[x];
        //printf("Dif - %dn", differ);
        //printf("Unfair - %dn", unfairness);
        if (unfairness == 0){
            unfairness = differ;
        }
        else if (differ<unfairness)
            unfairness = differ;
    }
    printf("%d", unfairness);
    return 0;
}