#include <fstream>
#define N 5000001
using namespace std;
 
FILE *fin=fopen("deque.in", "r"), *fout=fopen("deque.out", "w");
 
int a[N], b[N];
 
int main()
{
    int n, k, m1=1, m2=0, i;
    long long s=0;
    fscanf(fin, "%d%d", &n, &k);
    for(i=1;i<=n;i++)
    {
        fscanf(fin, "%d", &a[i]);
    }
    for(i=1;i<=n;i++)
    {
        while(m1<=m2&&a[i]<=a[b[m2]]) m2--;
        b[++m2]=i;
        if(b[m1]==i-k) m1++;
        if(i>=k) s+=a[b[m1]];
    }
    fprintf(fout, "%lld", s);
}