n,m,p,*a=map(int,open(0).read().split())
a.sort(reverse=True)
for i in a:
    if i%p!=0 and i!=1:
        break
x=1
j=0
while x<=m:
    if x*max(a)>m:
        print(j+1)
        exit(0)
    elif i%p==0 or i==1:
        print(-1)
        exit()
    x*=i
    j+=1
print(j)