#include<stdio.h>
#include<deque>
using namespace std;

#define NMAX 5000010

FILE*f=fopen("deque.in","r");
FILE*g=fopen("deque.out","w");

int n, k, a[NMAX];
long long s;
deque<int> d;

void read() {
    fscanf(f,"%d%d",&n,&k);
    for(int i = 1; i <= n; i++) fscanf(f, "%d", &a[i]);
}

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

    fprintf(g,"%lld",s);
}

int main() {

    read();
    solve();

    return 0;
}