#include <bits/stdc++.h>
using namespace std;
ifstream fin ("deque.in");
ofstream fout ("deque.out");
deque <int> dq;
int n,k,a[5000002];
long long sum=0;

int main()
{
    fin>>n>>k;
    for(int i=1;i<=n;++i)
        fin>>a[i];
    for(int i=1;i<=n;++i){
        while(!dq.empty() && dq.back()>=a[i])dq.pop_back();
        dq.push_back(a[i]);
        if(i-k>=1 && dq.front()==a[i-k])dq.pop_front();
        if(i>=k)sum+=dq.front();
        sum=sum+1-1;
    }
    fout<<sum;
    return 0;
}