#include<fstream>
#define NMAX 5000010 
using namespace std; 
int V[NMAX], Deque[NMAX], P,U,N,K; 
long long S; 
int main() 
{ 
ifstream f("deque.in"); 
ofstream g("deque.out"); 
int i; 
f>>N>>K; 
for(i=1;i<=N;i++) 
f>>V[i]; 
P=1;U=0; 
for(i=1;i<=N;i++) 
{ 
while((P<=U)&& V[i]<=V[Deque[U]]) 
U--; 
Deque[++U]=i; 
if(Deque[P]==i-K) P++; 
if(i>=K)  
S+=V[Deque[P]]; 
} 
g<<S; 
return 0; }