#include <cstdio>
#include <deque>
#include <vector>

using namespace std;

long long S;
deque <int> dq;
int v[5000005];

int main(){
    freopen("deque.in", "r", stdin);
    freopen("deque.out", "w", stdout);
    int n,k,i;
    scanf("%d%d",&n,&k);
    
    for(i=1;i<=n;++i){
        scanf("%d",&v[i]);
    }
    
    for(i=1;i<=n;++i){
        while(!dq.empty()&&v[dq.back()]>=v[i]){
            dq.pop_back();
        }
        dq.push_back(i);
        if(i-dq.front()==k){
            dq.pop_front();
        }
        if(i>=k){
            S+=v[dq.front()];
        }
    }
    printf("%lld\n",S);
    return 0;
}