#include <fstream>
using namespace std;

ifstream f("deque.in");
ofstream g("deque.out");
int v[100],m,n,i,j,mn,mn2,s,mn1,mn3,a[256][256],x;

int mn4(int i ,int j , int k, int l)
{
    if(a[i][j]<a[k][l])return a[i][j];
    else return a[k][l];

}

int main()
{
    f>>n>>m;
    mn2=mn=9999999;
    for(i=1;i<=n;i++)
    {
        f>>x;
        a[1][i]=x;
    }
    for(i=2;i<=n;i++)
    {
        for(j=1;j<=n;j++)
            a[i][j]=mn4(i-1,j,i-1,j-1);
    }


    for(j=m;j<=n;j++)
        s=s+a[m][j];
    g<<s<<endl;
    return 0;
}