#import<fstream>
std::ifstream f("deque.in");std::ofstream g("deque.out");int n,k,i=1,j,Q[5000005],a[5000005],L,R;long long s;main(){
for(f>>n>>k;i<=n;i++){
for(f>>a[i];L<=R&&a[Q[R]]>=a[i];R--);;
Q[++R]=i;if(i-Q[L]==k)L++;if (i>=k)s+=a[Q[L]];}
g<<s;}