#include <bits/stdc++.h>
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
int n,k,v[5000003],d[5000003],p,u;
long long s;
int main()
{fin>>n>>k;
for(int i=1;i<=n;i++)
{fin>>v[i];
}
d[1]=1;
u=p=1;
for(int i=2;i<=n;i++)
{while(p<=u && v[i]<=v[d[u]])u--;
u++;d[u]=i;
if(i-d[p]==k)p++;
if(i>=k)s+=v[d[p]];
}
fout<<s;
return 0;
}