#include <fstream>
#include <deque>
#include <cstdio>

#define NMax 5000005
using namespace std;

int n,k;
int a[NMax],q[NMax];
deque<int> deq;

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]);
    }
    long long s = 0;
    for(int i = 1; i <= n; ++i){
        while(!deq.empty() && a[i] <= a[deq.back()])
            deq.pop_back();
        deq.push_back(i);
        if(deq.front() <= i - k)
            deq.pop_front();
        if(i >= k)
            s += a[deq.front()];
    }
    printf("%lld",s);
    return 0;
}