#include <bits/stdc++.h>
using namespace std;

int main()
{
    ifstream cin("deque.in");
    ofstream cout("deque.out");
    deque <int> dq;
    vector <int> v;
    vector <int> minn;
    long long int n, k, sum=0;
    cin >> n >> k;
    v.resize(n);
    minn.resize(n);
    for(int i=0; i<n; i++)
        cin >> v[i];
        
    for(int i=0; i<k; i++)
    {
        while(!dq.empty() && v[dq.back()]>v[i])
            dq.pop_back();
        dq.push_back(i);
    }
    minn[0]=v[dq.front()];
    
    for(int i=k; i<n; i++)
    {
        if(dq.front()<=i-k)
            dq.pop_front();
        
        while(!dq.empty() && v[dq.back()]>v[i])
            dq.pop_back();
        dq.push_back(i);

        
        minn[i-k+1]=v[dq.front()];
    }
    
    for(int i=0; i<n; i++)
        sum+=minn[i];
        
    cout << sum;

    return 0;
}