#include<cstdio>
#include<queue>
#define BM 5000005
using namespace std;
deque <int> c;
int a[BM];
int main () {
    int n,k,i;
    long long s=0;
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d %d",&n,&k);
    for(i=1;i<=n;++i)scanf("%d",&a[i]);
    for(i=1;i<=n;++i){
        if(!c.empty())for(;(!c.empty())&&a[c.back()]>a[i];c.pop_back());
        c.push_back(i);
        if(c.front()<=i-k)c.pop_front();
        if(i>=k)s+=a[c.front()];
    }
    printf("%lld",s);
    return 0;
}