Problem:
Score : 300 points

Problem Statement

In some other world, today is Christmas Eve.

There are N trees planted in Mr. Takaha's garden. The height of the i-th tree (1 \leq i \leq N) is h_i meters.

He decides to choose K trees from these trees and decorate them with electric lights. To make the scenery more beautiful, the heights of the decorated trees should be as close to each other as possible.

More specifically, let the height of the tallest decorated tree be h_{max} meters, and the height of the shortest decorated tree be h_{min} meters. The smaller the value h_{max} - h_{min} is, the better. What is the minimum possible value of h_{max} - h_{min}?

Constraints

2 \leq K < N \leq 10^5

1 \leq h_i \leq 10^9

h_i is an integer.

Input

Input is given from Standard Input in the following format:

N K
h_1
h_2
:
h_N

Output

Print the minimum possible value of h_{max} - h_{min}.

Sample Input 1

5 3
10
15
11
14
12

Sample Output 1

2

If we decorate the first, third and fifth trees, h_{max} = 12, h_{min} = 10 so h_{max} - h_{min} = 2. This is optimal.

Sample Input 2

5 3
5
7
5
7
7

Sample Output 2

0

If we decorate the second, fourth and fifth trees, h_{max} = 7, h_{min} = 7 so h_{max} - h_{min} = 0. This is optimal.

There are not too many trees in these sample inputs, but note that there can be at most one hundred thousand trees (we just can't put a sample with a hundred thousand lines here).

Solution in C++14 (GCC 5.4.1) (judge verdict: Accepted)

#include <bits/stdc++.h>
using namespace std;

#define IOS cin.tie(0);ios_base::sync_with_stdio(false)

#define ll      long long
#define Fi      first
#define Se      second
#define Pb      push_back
#define vi      vector<int>
#define vs      vector<string>
#define vp      vector<pair<int,int>>
#define vvi     vector<vector<int>>
#define vvp     vector<vector<pair<int,int>>>
using Graph  =  vector<vector<int>>; //Caution!! Segmentation Fault!! Don't forget to add +1!

#define sz(x) (int)x.size()
#define all(v) v.begin(),v.end()
#define output_s(s) printf("%s\n",(s).c_str())

#define rep(i,n)        for(int i=0;i<(int)(n);i++)
#define Rep(i,n,m)      for(int i=(int)(n);i<(int)(m);i++)
#define RepS(i,n,m)     for(int i=(int)(n);i<=(int)(m);i++)
#define RRepS(i,n,m)    for(int i=(int)(n);i>=(int)(m);i--)
#define SRepS(i,n,m)    for(int i=(int)(n);i*i<=(int)(m);i++)
#define RepA(x)         for(auto &item:(x))

void CINT(){} //@shibh308's template
template<class Head,class... Tail> void CINT(Head&& head,Tail&&... tail){cin>>head; CINT(move(tail)...);}    
#define CIN(...) int __VA_ARGS__;CINT(__VA_ARGS__)
#define LCIN(...) ll __VA_ARGS__;CINT(__VA_ARGS__)
#define SCIN(...) string __VA_ARGS__;CINT(__VA_ARGS__)
#define VCIN(x) for(auto &item:x) cin>>item

void OUT(){}
template<class Head,class...Tail> void OUT(Head&& head,Tail&&...tail){cout<<head<<(sizeof...(tail)?" ":"\n"); OUT(move(tail)...);}
#define COUT(...) OUT(__VA_ARGS__)

template<typename TypeInt>TypeInt GCD(TypeInt a,TypeInt b){return a%b==0?b:GCD(b,a%b);} //最大公約数
template<typename TypeInt>TypeInt LCM(TypeInt a,TypeInt b){return a*b/GCD(a,b);} //最小公倍数
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;}
template<class T>bool comp(T a,T b){return abs(a)<abs(b);} //比較関数

void YES(bool f){printf(f?"YES\n":"NO\n");}
void Yes(bool f){printf(f?"Yes\n":"No\n");}
void Possible(bool f){printf(f?"Possible\n":"Impossible\n");}
void POSSIBLE(bool f){printf(f?"POSSIBLE\n":"IMPOSSIBLE\n");}

//----------------------library------------------------//

//const int dx[4]={1,0,-1,0};
//const int dy[4]={0,1,0,-1};
const int dx[8]={1,0,-1,0,1,-1,-1,1};
const int dy[8]={0,1,0,-1,1,1,-1,-1};
const int NMAX = 200;
const int INF = 1e9;
const int MOD = 1e9+7;
bool flag;

//----------------------Global-------------------------//

signed main(){
    CIN(N,K);
    vi H(N);VCIN(H);
    sort(all(H));
    int ans=INF;
    rep(i,N-K+1){
        int cur=H[i+K-1]-H[i];
        chmin(ans,cur);
    }
    printf("%d\n",ans);

    return 0;
}