#include <cstdio>
const int MAXN = 5000005;
int A[MAXN], Deque[MAXN],n,k;
long long s;
int main()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    scanf("%d %d", &n, &k);
    for(int i = 1; i <= n; ++i)
        scanf("%d", A+i);
    int Front = 1, Back = 0;
    for(int i = 1; i <= n; i++){
        while(Front <= Back && A[i] <= A[Deque[Back]]) Back--;
        Deque[++Back] = i;
        if(Deque[Front] <= i-k)
            Front++;
        if(i >= k) s += A[Deque[Front]];
    }
    printf("%lld", s);
    return 0;
}