#include <fstream>
#include <set>
#include <algorithm>
#define INF (2000000000)
using namespace std;

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

multiset<int, less<int> > x;
multiset<int, less<int> >::iterator it;

int n,i,k,v[5000200];
long long s;


int main()
{
    in>>n>>k;
    for(i=1; i<=n; i++)
    {
        in>>v[i];
        x.insert(v[i]);
        if(i == k)
            s += *(x.begin());
        if(i>k)
        {
            x.erase(x.find(v[i-k]));
            s += *(x.begin());
        }
    }
    out<<s;

    return 0;
}