from heapq import heappop,heappush
def main1(n,m,p,a):
  d={}
  mxv=0
  for x in a:
    mxv=max(mxv,x)
    cnt=1
    while x%p==0:
      cnt+=1
      x//=p
    if x==1:continue
    if cnt in d:d[cnt]=max(d[cnt],x)
    else:d[cnt]=x
  if mxv>m:return 1
  if len(d)==0:return -1
  todo=[[0,1]]
  costary=[0]*1000
  costary[0]=1
  ans=float('inf')
  while todo:
    c,v=heappop(todo)
    if costary[c]>v:continue
    if v>m:
      ans=min(ans,c)
      continue
    if v*mxv>m:
      ans=min(ans,c+1)
      continue
    for key,value in d.items():
      if costary[c+key]<v*value:
        costary[c+key]=v*value
        heappush(todo,[c+key,v*value])
  return ans

if __name__=='__main__':
  n,m,p=map(int,input().split())
  a=list(map(int,input().split()))
  ret1=main1(n,m,p,a)
  print(ret1)