#include <cstdio>
#include <deque>
using namespace std;
deque <int> S;
deque <int> P;
int n,k,i,x;
long long s;
int main()
{freopen("deque.in","r",stdin);
 freopen("deque.out","w",stdout);
 scanf("%d%d",&n,&k);
 for(i=1;i<=n;++i)
    {scanf("%d",&x);
     while(S.size()>0&&x<=S.back())
          {S.pop_back();
           P.pop_back();
          }
     if(P.size()>0&&P.front()<=i-k){S.pop_front();P.pop_front();
                     }
     S.push_back(x);
     P.push_back(i);
     if(i>=k){s=s+S.front();}
    }
 printf("%lld",s);
}