#include "bits/stdc++.h"
#define wsp                cin >> ws;
#define sp                 setprecision
#define sz                 size()            
#define sn(n)              scanf("%lld",&n)
#define cn(n)              cin>>n
#define pr(n)              printf("%lld\n",n)
#define ff                 first
#define ss                 second
#define prn                cout<<endl
#define str(n)             scanf("%s",n)
#define pb                 push_back
#define len(n)             n.length()
#define forp(i,a,b)        for(ll i=a;i<=b;i++)
#define rep(i,n)           forp(i,0,n-1)
#define forn(i,a,b)        for(ll i=a;i>=b;i--)
#define ren(i,n)           forn(i,n-1,0)
#define LALIT              ios_base::sync_with_stdio(false);cin.tie(0)
#define tr(container, it)  for(__typeof(container.begin()) it = container.begin(); it != container.end(); it++)
#define mem(n,m)           memset(n,m,sizeof(n))
#define mp                 make_pair
#define mod                1000000007                                                                             

using namespace std;
typedef unsigned long long int ull;
typedef long long int          ll;
typedef pair<int, int>         pii;
typedef pair<ll, int>          pli;
typedef pair<double, int>      pdi;
typedef pair<ll, ll>           pll;
typedef pair<double, double>   pdd;
const int  N = int(300000)+5;
 
template<typename T,typename T1>
void prin(vector<pair<T,T1> >& a)
{
    rep(i,a.size())
    {
        cout << a[i].fi<<" "<<a[i].se<<"\n";
    }
}
 
 
 
template<typename T>
void prin_new_line(vector<T>& a)
{
     rep(i,a.size())
    {
        cout << a[i]<<"\n";
    }
}
 
template<typename T,typename T1>
void prin_new_line(vector<pair<T,T1> >& a)
{
   rep(i,a.size())
    {
        cout << a[i].fi<<" "<<a[i].se<<"\n";
    }
}
 
template<typename T>
T max(vector<T>& a)
{
    T ans=a[0];
    rep(i,a.size())
    {
        ans=max(ans,a[i]);
    }
    return ans;
}
 
template<typename T>
T min(vector<T>& a)
{
    T ans=a[0];
   rep(i,a.size())
    {
        ans=min(ans,a[i]);
    }
    return ans;
}
 
template<typename T>
T min(T a,T b,T c)
{
    return min(a,min(b,c));
}
 
template<typename T>
T max(T a,T b,T c)
{
    return max(a,max(b,c));
}
 
long double s_triangle(long double x1,long double y1,long double x2,long double y2,long double x3,long double y3)
{
    return abs(((x2-x1)*(y3-y1)-(x3-x1)*(y2-y1))/2);
}
 
bool overflow(ll a,ll b)
{
    if(a*b/b!=a)
        return true;
    return false;
}

ll t , n , m , k , c , remov , tot,sum  , r  , ans , cnt , cnt1 ,cnt2 ;

ll a[N] , b ;

int main()
 {
     LALIT;
     cin >> n >> k;
     rep(i,n)cin>>a[i];
     m=1e18;
     if(n==k)
     {
     	
     	rep(i,n)
		 {
		 m=min(m,a[i]);}
     	cout<<m;
	 }
	 rep(i,n)
	 {
	 	sum=a[i];
	 	for(ll j=i+k+1;j<=n;j+=k)
	 	{
	 		sum+=a[j];
		 }
	 	m=min(m,sum);
	 }
	 cout << m ;
 return 0;
}