#include <bits/stdc++.h>

using namespace std;
class InputReader
{
public:
    static const int BUFF_SIZE = 1 << 17;
    FILE *fin;
    int bp;
    char buff[BUFF_SIZE];
    InputReader (const char *file_name)
    {
        fin = fopen(file_name, "r");
        bp = BUFF_SIZE - 1;
    }
    void adv()
    {
        if (++bp == BUFF_SIZE)
        {
            fread(buff, sizeof(char), BUFF_SIZE, fin);
            bp = 0;
        }
    }
    InputReader& operator >> (int& num)
    {
        num = 0;
        int semn = 1;
        while (isdigit(buff[bp]) == false)
        {
            if (buff[bp] == '-')
                semn = -1;
            adv();
        }
        while (isdigit(buff[bp]))
        {
            num = num * 10 + buff[bp] - '0';
            adv();
        }
        num *= semn;
        return *this;
    }
};

InputReader fin("deque.in");
ofstream fout("deque.out");

int v[5000005];

deque < int > dq;

int main()
{
    int n, k, i;
    long long s = 0;

    fin >> n >> k;

    for (i = 1; i <= n; ++i)
        fin >> v[i];

    for (i = 1; i <= n; ++i)
    {
        while (!dq.empty() && v[dq.back()] >= v[i])
        {
            dq.pop_back();
        }
        dq.push_back(i);
        if (dq.front() == i - k)
            dq.pop_front();
        if (i >= k)
            s += (v[dq.front()]);
    }

    fout << s << '\n';

    return 0;
}