#include<fstream>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n, i, v[5000000], k, minim;
long long S;

int min( int a, int b )
{
    int c;
    if( a>b ) c = b;
    else c=a;
    return c;
}

int main()
{
    fin>>n>>k;
    for(i=1; i<=n; i++) fin>>v[ i ];
    minim = v[1];
    for(i=2; i<=k; i++) if( minim<v[i] ) minim = v[i];
    S += minim;
    for(i=k+1; i<=n; i++)
    {
                       minim = min( minim , v[i] );
                       S += minim;
                       }
    fout<<S;
    fin.close();
    fout.close();
    return 0;
}