#include <cstdio>
using namespace std;
int n,k,v[5000009],minn,sol[5000009],i,j;
long long s;
int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d %d",&n,&k);

    for (i=1;i<=n;i++)
        scanf("%d\n",&v[i]);
    
    s=0;
    for (i=1;i<=k;i++)
        sol[i]=v[i];
    minn=sol[1];

    j=k;
    do
    {
	minn=sol[1];
        for (i=1;i<=k;i++)
            if(minn>sol[i])
                minn=sol[i];
        s+=minn;
        for (i=1;i<=k;i++)
        {
            sol[i]=sol[i+1];
        }
        j++;
        sol[k]=v[j];
    }
    while(j<=n);
    printf("%d",s);
    return 0;
}