#include <bits/stdc++.h>
using namespace std;

#define endl "\n"
#define IOS ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);

typedef long long int ll;

ll mod=1e9+7;
ll a[200010];
ll b[200010];
ll tc,i,j,k,n,m;
string s,s1,s2;

map<ll,ll> mpi;
map<ll,ll> mpj;
vector<ll> v;

int main(){

    IOS
            cin>>n>>k;

            ll sum=0;
            for(i=0;i<n;i++){
                cin>>a[i];
                sum+=a[i];
            }

            ll mx=-100;
            for(i=0;i<n;i++){
                if((i-k)>=0)
                a[i]+=a[i-k];

                mx=max(mx,a[i]);
            }

            cout<<sum-mx<<endl;


}