def aa(s):
    global m,c
    if s>=m:
        return 0
    if s*c>=m:
         return 1
    if s in v:
        return v[s]
    res=1<<30
    for i in range(1,len(y)):
    	if y[i]:
    		res=min(res,aa(s*y[i])+i)
    v[s]=res
    return res


n,m,p=map(int,input().split())
a=list(map(int,input().split()))
x={};c=max(a)
for i in a:
    d=1
    while i%p==0:
        i//=p;d+=1
    if i==1:
        continue
    if i in x:
        x[i]=min(x[i],d)
    else:
        x[i]=d
if len(x)==0:
    print(-1)
    exit()
y=[0]*61
for i,j in x.items():
	y[j]=max(y[j],i)
v={}
aa(1);print(v[1])