n0,m0,v0,p0,*a0=$<.read.split.map &:to_i
as=a0.sort_by{|e|-e}
th=as[p0-1]
a1=as.drop(p0)
v1=[v0-p0,0].max
n1=n0-p0
ans=p0
tsum=0
a1.each_with_index{|e,i|
  break if th>e+m0 || i>=n1-v1 && tsum+(1+v1-n1)*m0>e*i
  tsum+=e
  ans+=1
}
p ans
