#include <iostream>
#include <set>
using namespace std;

struct hegy{
    long long magassag, ar;
};

int main(){
    multiset<long long> ms;
    long long mini=1000000000000000, osszeg=0;
    long long n, k, x, y, m=1000000000;
    cin >> n >> k;
    hegy a[n];
    /*for(int i=0; i<n; i++){
        cin >> a[i].magassag;
        a[i].ar=m-a[i].magassag;
        osszeg+=a[i].ar;
        m++;
        ms.insert(a[i].ar);
        if(ms.size()==k){
            x=osszeg-k*(*ms.begin());
            cout << i+1 << ":\nosszeg: " << osszeg << "\nmin: " << (*ms.begin()) << "\nk: " << k <<  "\nk*(*ms.begin())" << k*(*ms.begin()) << "\nx: " << x << "\n\n";
            if(x<mini) mini=x;
            ms.erase(ms.find(a[i-k+1].ar));
            osszeg-=a[i-k+1].ar;
        }
    }*/
    ms.clear();
    m=2000000000;
    osszeg=0;
    for(int i=0; i<n; i++){
        cin >> a[i].magassag;
        a[i].ar=m-a[i].magassag;
        osszeg+=a[i].ar;
        m--;
        ms.insert(a[i].ar);
        if(ms.size()==k){
            x=osszeg-k*(*ms.begin());
            //cout << i+1 << ":\nosszeg: " << osszeg << "\nmin: " << (*ms.begin()) << "\nk: " << k <<  "\nk*(*ms.begin())" << k*(*ms.begin()) << "\nx: " << x << "\n\n";
            if(x<mini) mini=x;
            ms.erase(ms.find(a[i-k+1].ar));
            osszeg-=a[i-k+1].ar;
        }
    }
    cout << mini;
    return 0;
}