#include<iostream>
#include<stdio.h>
#include<deque>
int n,i,x,k,s;
deque <int> Q;
int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    scanf("%d%d",&n,&k);
    for(i=0;i<n;i++)
    {
        scanf("%d",&x);
        while(!Q.empty()&&Q.back()>x)
            Q.pop_back();
        if(Q.size()<k)
            Q.push_back(x);
        if(i+1==k)
        {
            s+=Q.front();
            Q.pop_front();
        }
    }
    printf("%d\n",s);
    return 0;
}