#include<stdio.h>
#include<deque>
#include<vector>
using namespace std;
int n,i,x,k,s;
deque <int> Q;
vector <int> a;
int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d%d",&n,&k);
    for(i=0;i<n;i++)
    {
        scanf("%d",&x);
        a.push_back(x);
    }
    for(i=0;i<n;i++)
    {
        while(!Q.empty()&&a[Q.back()]>a[i])
            Q.pop_back();
        Q.push_back(i);
        if(Q.front()==i-k+1)
            Q.pop_front();
        if(i-1>=k)
            s+=a[Q.front()];
    }
    printf("%d\n",s);
    return 0;
}