#include <bits/stdc++.h>

using namespace std;

int N, K;
deque <int> dq;
int *v;

inline int read()  {
    int x = 0, sm = 1;
    char ch = getchar();
    while(ch != '-' && !isdigit(ch))
        ch = getchar();
    if(ch == '-')  {
        ch = getchar();
        sm = -1;
    }
    while(isdigit(ch))  {
        x = x * 10 + ch - '0', ch = getchar();
    }
    return x * sm;
}

int main()  {
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    N = read(), K = read();
    v = new int[N + 1];
    for(int i = 1;i <= N;i++)
        v[i] = read();
    long long sum = 0LL;
    for(int i = 1;i <= N;i++)  {
        int val;
        val = v[i];
        while(dq.size() && v[dq.back()] >= val)
            dq.pop_back();
        dq.push_back(i);
        if(dq.front() == i - K)
            dq.pop_front();
        if(i >= K)
            sum += 1LL * v[dq.front()];
    }
    cout << sum;
    return 0;
}