#include <iostream>
#include <fstream>
using namespace std;
ifstream f("deque.in");
ofstream g("deque.out");

int main()
{int n,k,i,x[510000],minn,j;
long long s=0;
    f>>n>>k;
    for(i=1;i<=n;i++)
        f>>x[i];
i=1;
while(i<=n-k+1)
{   minn=x[i];
    for(j=i;j<=i+k-1;j++)
    {   if(j<=n)
        if(x[j]<minn)
            minn=x[j];
    }
    s=s+minn;
    i++;
}


       g<<s;
        return 0;
}