#include <cstdio>
#include<iostream>
using namespace std;
int v[5000002],d[5000002];
int main()
{
    int n,k,i;
    long long s=0;
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d%d",&n,&k);
    for(i=1;i<=n;i++)
        scanf("%d",&v[i]);
    int p=1,u=0;
    for(i=1;i<=n;i++)
    {
        while(p<=u&&v[d[u]]>=v[i])
            u--;
        u++;
        d[u]=i;
        if(d[p]<i-k+1)
            p++;
        if(i>=k)
            s+=v[d[p]];
    }
    cout<<s;
    return 0;
}