#include<fstream>
#include<iostream>
#include<climits>
#include<algorithm>
#include<cstring>
#include<cmath>

using namespace std;

//ifstream f("in.in");
//ofstream g("out.out");

ifstream f("deque.in");
ofstream g("deque.out");

long n,k,st=0,dr=1,v[5000005],s[5000005];

long long sum=0;

int main()
{
    f>>n>>k;
    for(int i=1;i<=n;i++)
    {
        f>>v[i];
        while(st>=dr&&v[s[st]]>=v[i])
            st--;
        st++;
        s[st]=i;

        if(i-s[dr]+1>k)
            dr++;



        if(i>=k)
        {
            sum+=v[s[dr]];
            //cout<<i<<" "<<v[s[dr]]<<'\n';
        }
    }
    g<<sum;
    f.close();
    g.close();
    return 0;
}