#include <bits/stdc++.h>

using namespace std;

const int NMAX = 5000000;

int v [NMAX + 5];
deque <int> d;

int main() {
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    int n,k;
    long long s=0;
    scanf("%d%d",&n,&k);
    for(int i=1; i<=n; i++) {
        scanf("%d",&v[i]);
        while (!d.empty() && v[d.back()] >= v[i])
            d.pop_back();
        d.push_back(i);
        if(i-d.front()==k)
            d.pop_front();
        if(i>=k)
            s+=v[d.front()];
    }
    printf("%lld\n",s);
}