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
for j in range(10**7):
    if x*a[0]>m:
        print(j+1)
        exit(0)
    x*=i
    if x%p==0:
        x//=p
print(-1)