#include <fstream>

using namespace std;
ifstream in("deque.in");
ofstream out("deque.out");
const int N=5e6;
int dq[N+1],v[N+1];
int p=0,u=0;
int main()
{
     int n,k,i;
     in>>n>>k;
     for(i=1;i<=n;i++)
        in>>v[i];
     long long ans=0;
     p = 1;
     for(i=1;i<=n;i++){
         while(p && u && p<=u&&i-dq[p]>=k)
            ++p;
         while(p && u && p<=u&&v[dq[u]]>=v[i])
            --u;
         dq[++u]=i;
         if(i>=k) {
            ans = ans + v[dq[p]];
         }
     }
     out << ans << "\n";
    return 0;
}