#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int A[5000010],deque2[5000010];
int main()
{
    int n,k,Back = 0,Front = 1;
    long long sum=0;
    fin>>n>>k;
    for(int i = 1;i<=n;i++)
        fin>>A[i];
    for(int i = 1;i<=n;i++)
    {
        while(Front<=Back && A[deque2[Back]] >= A[i]) Back--;
        deque2[++Back] = i;
        if(deque2[Front]<=i-k) Front++;
        if(i>=k) sum+=A[deque2[Front]];
    }
    fout<<sum;
    return 0;
}