#include <bits/stdc++.h>
using namespace std;
const string file="deque";
ifstream f(file+".in");
ofstream g(file+".out");
//#define f cin
//#define g cout
int n,k,x,m=INT_MAX;
long long s;
deque<int>d;
vector<int>v;
int main(){
    f>>n>>k;
    v.resize(n+1);
    for(int i=1; i<=n; ++i) f>>v[i];
    d.push_back(1);
    for(int i=2; i<=n; ++i){
        while(!d.empty() && v[i]<=v[d.back()])
            d.pop_back();
        d.push_back(i);
        if(i-d.front()==k) d.pop_front();
        if(i>=k) s+=v[d.front()];
    }
    g<<s;
    return 0;
}