N,M,P=map(int,input().split())
A=list(map(int,input().split()))
B=[]
C=[]
for i in range(N):
  B.append(A[i])
  C.append(1)
  while B[i]%P==0:
    B[i]//=P
    C[i]+=1
Z=max(A)
X=(M+Z-1)//Z
if max(B)==1 and X>1:
  print(-1)
  exit()
D=[[B[i],C[i]] for i in range(N)]
D.sort(key=lambda x:((x[0]**10)**(1/x[1])))
P=0
Y=1
while Y*Z<=M:
  Y*=D[-1][0]
  P+=D[-1][1]
print(P+1)