#include <stdio.h>  
  
#define maxn 5000010  
#define inf 1000000000  
  
int N, K;  
int A[maxn];  
long long Sum;  
  
int main()  
{  
    freopen("deque.in", "r", stdin);  
    freopen("deque.out", "w", stdout);  
  
    int i, j, p = 0, best;  
  
    scanf("%d %d ", &N, &K);  
  
    for (i = 1; i <= N; i++) scanf("%d ", &A[i]);  
  
    best = inf;  
    for (i = 1; i <= N; i++)  
    {  
        if (A[i] <= best) best = A[i], p = i;  
  
        if (p <= i-K)  
        {  
            best = inf, p = 0;  
            for (j=0; j<K; j++)  
                if (A[i-j] < best) best = A[i-j], p = i-j;  
        }  
  
        if (i >= K) Sum += best;  
    }  
  
    printf("%lld\n", Sum);  
  
    return 0;  
}