#include<fstream.h>
int N,K,A[5000001],d[5000001],p=1,u,i=1;
long long s;
int main()
{ifstream f("deque.in");
ofstream g("deque.out");
f>>N>>K;
for(;i<=N;++i)
{f>>A[i];
 for(;p<=u&&A[i]<=A[d[u]];--u);
 d[++u]=i;
 if(d[p]==i-K)p++;
 if(i>=K)
  s+=A[d[p]];
}
g<<s;
return 0;
}