link

code:

#include<bits/stdc++.h>
using namespace std;
int n,k,a[1000030];
int s1[1000030],s2[1000030];
int main(){
    cin>>n>>k;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    sort(a+1,a+1+n);
    for(int i=1;i<=n;i++){
        s1[i]=s1[i-1]+a[i];
        s2[i]=s2[i-1]+a[i]*a[i];
    }
    int t=(k-1)/2+1,t1=k/2,ans=0x7fffffff;
    for(int i=t+1;i<=n-t+1;i++){
        int l=i-t1,r=i+t-1,sum=0;
        for(int j=l;j<=r;j++){
            sum+=(a[j]-a[i])*(a[j]-a[i]);
        }
        ans=min(ans,sum);
    }
    cout<<ans;
}