#include<stdio.h>
FILE *fin=fopen("deque.in","r");
FILE *fout=fopen("deque.out","w");
long long s;
int n,k,v[5000005],i,p,u,d[5000005];

int main(){

    fscanf(fin,"%d %d",&n,&k);
    p=1;
    u=1;
    d[1]=1;
    fscanf(fin,"%d",&v[1]);

    for(i=2;i<=n;i++){
        fscanf(fin,"%d",&v[i]);

        while(p<=u && v[d[u]]>=v[i]){
            u--;
        }
        d[++u]=i;

        if(i-d[p]==k){
            p++;
        }
        if(i>=k){
            s+=v[d[p]];
        }
    }

    fprintf(fout,"%lld",s);

return 0;
}