#include <cstdio>
#include <deque>
#include <iostream>

using namespace std;

#define NMAX 5000002

int sir[NMAX];
deque<int> pos;

int n, k;
long long sum;

void calc_min(){
    for(int i = n; i >= 1; --i){
        while(!pos.empty() && sir[pos.back()] >= sir[i])
            pos.pop_back();
        if(!pos.empty() && pos.front() == k + i)
            pos.pop_front();
        pos.push_back(i);
        if(i <= n - k + 1)
            sum += sir[pos.front()];
    }
    printf("%lld", sum);
}


int main()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    scanf("%d%d", &n, &k);
    for(int i = 1; i <= n; ++i)
        scanf("%d", &sir[i]);
    calc_min();
    return 0;
}