#include <stdio.h>
int pr,ul,i,n,k,deque[5000000],t[5000000];
long long s;
int main(){
freopen("deque.in","r",stdin);
freopen("deque.out","w",stdout);
scanf("%d%d",&n,&k);
for (i=1;i<=n;i++) scanf("%d",&t[i]);
pr=1; ul=0; s=0;
for (i=1;i<=n;i++) {
while (pr<=ul && t[deque[ul]]>=t[i]) ul--;
ul=ul+1; deque[ul]=i;
if (i-deque[pr]==k) pr++;
if (i>=k) s+=t[deque[pr]];
}
printf("%lld",s);
return 0;
}