#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define lld I64d
int main()
{;
int m,n;
cin>>n>>m;
int arr[m];
for (int i = 0; i < m; ++i)
{
/* code */
cin>>arr[i];
}
sort(arr,arr+m);
int ans = 100000;
for(int i =0;i+n-1<m;i++)
{
ans = min(ans,arr[i+n-1]-arr[i]);
}
cout<<ans;
}
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