#include<stdio.h>
int main()
{
    int n,m,i,a[1000],sum =0;
    float c;
    scanf("%d %d",&n,&m);
    for(i=0;i<n;i++){
        scanf("%d",&a[i]);
        sum+=a[i];

    }
    c = (.25/m)*sum;
    if(c<a[m-1])printf("YES\n");
        else printf("NO\n");
    return 0;
}
