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

ifstream f("deque.in");
ofstream g("deque.out");
int n,k,i=1,j,fr,m,sum;

int main() {
    f >> n >> k;
    int d[n];
    f>>d[m];
    int mn=d[m];
    while(i<=n)
    {

        for(j=fr;j<=m;j++)
        {
            if (d[j] < mn)
            {
                mn = d[j];
            }
        }
        if(i>=k)
        {
            sum+=mn;
            fr++;
            mn=d[fr];
        }
        i++;
        m++;
        f>>d[m];
    }
    g<<sum;

    return 0;
}