#include <bits/stdc++.h>
using namespace std;
#define ST          first
#define ND          second
#define PB          push_back
#define MKP         make_pair
#define LWBND		lower_bound
#define UPBND		upper_bound
#define FOR(i,a,b)  for(int i=(a);i<=(b);++i)
#define FORS(i,a,b) for(int i=(a);i<(b);++i)
#define ALL(x)      x.begin(),x.end()
#define SZ(x)       ((int)(x).size())
#define MOD         1000000007 //998244353
#define MAXN        200005
typedef long long ll;
typedef pair<int,int> PII;
typedef vector<int> VI;
typedef vector<PII> VPII;
const int INF=0x3f3f3f3f;

ll n,k,x,ans;
deque<PII> mini;

int main()
{
    freopen("deque.in","r",stdin);
    freopen("deque.out","w",stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cin>>n>>k;
    FOR(i,1,n){
        cin>>x;
        while(!mini.empty()&&mini.back().ST>=x)
            mini.pop_back();
        mini.PB({x,i});
        if(mini.front().ND<=i-k)
            mini.pop_front();
        if(i>=k)
            ans+=mini.front().ST;
    }
    cout<<ans;
}