#include <cstdio>
        #include <deque>
        using namespace std;
        deque <int> h;
        int a[5000001];
        int main()
        {
            int n, k, i;
            signed long long int 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++)
            {
                while(!h.empty() && a[h.back()]>a[i])
                {
                    h.pop_back();
                }
                h.push_back(i);
                while(h.front()<=i-k)
                {
                    h.pop_front();
                }
                if(i>=k) s+=a[h.front()];
            }
            printf("%lld",s);
            fclose(stdin);
            fclose(stdout);
            return 0;
        }