import sys
input=sys.stdin.readline

N,M,P=map(int,input().split())
A=set(map(int,input().split()))
A=list(A)

Max=max(A)

T={}
for b in A:
    a=b
    m=1
    while b%P==0:
        b//=P

    if b>1 and ((b not in T) or (T[b]>m)):
        T[b]=m

if (not T) and Max<=M:
    print(-1)
    exit(0)

Memo={}

def f(x):
    if x in Memo:
        return Memo[x]
    elif x>M:
        return 0
    elif x*Max>M:
        return 1

    X=float("inf")
    for b in T:
        m=T[b]
        X=min(X,f(x*b)+m)
    Memo[x]=X
    return X
print(f(1))