#include <bits/stdc++.h>
using namespace std;ifstream f("deque.in");ofstream g("deque.out");int v[5000007],n,k,i;long long s;deque<int>q;int main(){f>>n>>k;for(i=1;i<=n;i++){f>>v[i];while(!q.empty()&&v[i]<=v[q.back()])q.pop_back();q.push_back(i);if(q.front()==i-k)q.pop_front();if(i>=k)s+=v[q.front()];}g<<s;return 0;}