#include<bits/stdc++.h>
using namespace std;ifstream fin("deque.in");ofstream fout("deque.out");int n,k,i,x;long long s;int main(){fin>>n>>k;deque<pair<int,int>>d;for(i=1;i<=n;i++){fin>>x;while(!d.empty()&&d.back().first>x)d.pop_back();d.push_back({x,i});while(d.front().second+k-1<i)d.pop_front();if(d.back().second>=k)s+=d.front().first;}fout<<s;}