#include<bits/stdc++.h>

using namespace std;

#define boost ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0)
#define INF 1e18

typedef long long ll;
ll C[100001];
ll tree[300001];
ll tree1[300001];
ll dp1[100001];
ll dp2[100001];


void build(ll node, ll start,ll _end){
    if(start==_end){
        tree[node] = INF;
        return;
    }
    ll mid = (start+_end)>>1;
    build(2*node,start,mid);
    build(2*node+1,mid+1,_end);
}

void build1(ll node, ll start,ll _end){
    if(start==_end){
        tree1[node] = INF;
        return;
    }
    ll mid = (start+_end)>>1;
    build1(2*node,start,mid);
    build1(2*node+1,mid+1,_end);
}




void update(ll node, ll start, ll _end, ll idx){
    if(start == _end && start == idx){
        tree[node] = dp1[idx];
        return;
    }
    ll mid = (start+_end)>>1;
    if(idx <= mid)
         update(2*node,start,mid,idx);
    else
         update(2*node+1,mid+1,_end,idx);
    tree[node] =min(tree[2*node],tree[2*node+1]);
}


void update1(ll node, ll start, ll _end, ll idx){
    if(start == _end && start == idx){
        tree1[node] = dp2[idx];
        return;
    }
    ll mid = (start+_end)>>1;
    if(idx <= mid)
        update1(2*node,start,mid,idx);
    else
        update1(2*node+1,mid+1,_end,idx);
    tree1[node] =min(tree1[2*node],tree1[2*node+1]);
}



ll query(ll node, ll start, ll _end, ll qs, ll qe){
    if(start > _end || qs > _end || start > qe) return INF;
    if(start >= qs && _end <= qe)   return tree[node];
    ll mid = (start+_end)>>1;
    ll a = query(2*node,start,mid,qs,qe);
    ll b = query(2*node+1,mid+1,_end,qs,qe);
    return min(a,b);
    
}


ll query1(ll node, ll start, ll _end, ll qs, ll qe){
    if(start > _end || qs > _end || start > qe) return INF;
    if(start >= qs && _end <= qe)   return tree1[node];
    ll mid = (start+_end)>>1;
    ll a = query1(2*node,start,mid,qs,qe);
    ll b = query1(2*node+1,mid+1,_end,qs,qe);
    return min(a,b);
    
}







int main(){
    boost;
    ll T,N,i,j,k,M,m,n;
    ll K;
    cin >> N >> K;
    for(i = 0 ; i < N ; i++)
        cin >> C[i];
    build(1,0,N-1);
    build1(1,0,N-1);
    for(i = 0 ; i <= K && i < N; i++){
        dp1[i] = C[i];
        update(1,0,N-1,i);
    }
    
    for(i = K+1 ; i < N ; i++){
        dp1[i] =  C[i] + query(1,0,N-1,i-K,i-1);
    }
    
    for(i = N-1 ; i >= N-K-1 && i >= 0 ; i--){
        dp2[i] = C[i];
        update1(1,0,N-1,i);
    }
    
    for(i = N-K-2 ; i >= 0 ; i--){
        dp2[i] = C[i] + query1(1,0,N-1,i+1,i+K);
    }
    
    ll _min = INF;
   /* for(i = 0 ; i < N ; i++)
        cout << dp1[i]<<" ";
    cout << endl;
    for(i = 0 ; i < N ; i++)
        cout << dp2[i] <<" ";
    cout << endl;*/
    for(i = 0 ; i < N ; i++)
        _min = min(_min,dp1[i]+dp2[i]-C[i]);
    cout << _min << endl;
    
}