#include <iostream>
#include <fstream>
using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");
int n,k,a[5000003],i,nr,j,sum=0,m;
int main()
{
    in>>n>>k;
    for(i=1;i<=n;i++)
    {
        in>>a[i];
    }
    nr=1;
    while(k<=n)
    {
        m=a[nr];
        for(i=nr;i<=k;i++)
            if(m>a[i])
                m=a[i];
        sum=sum+m;
        k++;
        nr++;
    }
    out<<sum;
}