//#include <iostream>
#include <fstream>
using namespace std;

long long v[5000001],k,n,i,s=0;
int p,u,d[5000001];

void deque()
{
    p=1;
    u=0;
    for(i=1; i<=n; i++){
        while(p<=u && v[i]<=v[d[u]])u--;
        d[++u]=i;
        if(d[p]+k<=i)p++;
        if(i>=k)s+=v[d[p]];
    }
}

int main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    cin>>n>>k;
    for(i=1; i<=n; i++)
        cin>>v[i];
    deque();
    cout<<s;
    return 0;
}