#include <cstdio>

using namespace std;

int v[5000010],q[5000010];

int main()
{
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    int n,k,st=1,dr=0;
    long long sol=0;
    scanf("%d%d",&n,&k);
    for(int i=1;i<=n;i++) scanf("%d",&v[i]);
    for(int i=1;i<=n;i++)
    {
        while(st<=dr && v[q[dr]]>=v[i]) dr--;
        q[++dr]=i;
        if(q[st]<=i-k) st++;
        if(i>=k) sol+=v[q[st]];
    }
    printf("%lld",sol);
    return 0;
}