#include <cstdio>
        #include <vector>
        #include <set>
        using namespace std;
        multiset <int> h;
        multiset <int> :: iterator it;
        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<k; i++) h.insert(a[i]);
            for (i=k; i<=n; i++)
            {
                h.insert(a[i]);
                it=h.begin();
                s+=*it;
                h.erase(a[i-k+1]);
            }
            printf("%lld",s);
            fclose(stdin);
            fclose(stdout);
            return 0;
        }