#include <stdio.h>
#include <set>
using namespace std;
set<int> heap;
long i,k,n,v[5000005];
long long sum;
int main()
{
    FILE *f1,*f2;
    f1=fopen("deque.in","r");
    f2=fopen("deque.out","w");
    fscanf(f1,"%ld%ld",&n,&k);
    for(i=1;i<=n;i++)
    {
        fscanf(f1,"%ld",&v[i]);
        heap.insert(v[i]);
        if(i>k)
        {
            heap.erase(v[i-k]);
            sum+= *heap.begin();
        }
        else if(i==k)
            sum+= *heap.begin();
    }
    fprintf(f2,"%lld",sum);
    return 0;
}