#include <iostream>
#include <fstream>
#define dim 5000005
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n,k,i,st,dr;
long long sol;
int v[dim],d[dim];
int main()
{
   fin>>n>>k;
   st=1;
   dr=0;
   for(i=1;i<=n;i++){
        fin>>v[i];
        if(i-d[st]>=k)
            st++;
        while(dr>=st&&v[d[dr]]>=v[i])
            dr--;
        dr++;
        d[dr]=i;
        if(i>=k)
            sol+=v[d[st]];
   }
   fout<<sol;
}