#include <vector>
#include <algorithm>
#include <stdio.h>
#include <iostream>
using namespace std;
int main() {
int n,m,i,j,min= 2147483647;
scanf("%i %i",&n,&m);
vector<int>v(m);
for(i=0;i<m;i++)scanf("%i",&v[i]);
sort(v.begin(),v.end());
for(i=0;i+n-1<m;i++)if(v[i+n-1]-v[i]<min)min=v[i+n-1]-v[i];
printf("%i\n",min);
// your code goes here
return 0;
}
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