#include <stdio.h>
#include <deque>
using namespace std;
FILE*f=fopen("deque.in","r");
FILE*g=fopen("deque.out","w");
long long i,a[5000002],n,k;
deque <int> d;
long long s;
int main()
{
fscanf(f,"%lld%lld",&n,&k);
for(i=1;i<=n;i++){fscanf(f,"%lld",&a[i]);
    while(!d.empty()&&a[d.back()]>=a[i])
        d.pop_back();
    d.push_back(i);
    if(i-d.front()>=k)
        d.pop_front();
    if(i>=k) s+=a[d.front()];
}
fprintf(g,"%lld\n",s);



    return 0;
}