#include <cstdio>
#include <deque>
#define Lmax 5000000

using namespace std;

int n,k;
long long s=0;
int a[Lmax];

FILE *fin=freopen("deque.in","r",stdin);
FILE *fout=freopen("deque.out","w",stdout);

deque <int> c;

void ceva()
{
    for(int i=0;i<n;i++)
    {
        scanf("%d",&a[i]);
        while(!c.empty() && a[c.back()]>a[i])
            c.pop_back();
        c.push_back(i);
        if(c.front()<=i-k)
            c.pop_front();
        if(i>=k-1)
            s+=a[c.front()];
    }
}


int main()
{
    scanf("%d %d", &n, &k);
    ceva();
    printf("%lld\n",s);
    return 0;
}