#include <fstream>
#include <deque>
#include <vector>

#define ll long long

using namespace std;

ifstream cin ("deque.in");
ofstream cout ("deque.out");

ll n,m,i,a,sum=0;
deque <ll> v;

int main()
{
    cin>>n>>m;
    vector <ll> x(n+1);
    for (i=1;i<=n;++i)
    {
        cin>>x[i];
    }

    for (i=1;i<=n;++i)
    {
        while (!v.empty() && x[v.back()]>x[i]) v.pop_back();
        v.push_back(i);
        if (i>=m)
        {
            while (v[0]<=i-m) v.pop_front();
            sum+=x[v[0]];
        }
    }

    cout<<sum;
    return 0;
}