n, m, p = map(int, input().split())
A = list(map(int, input().split()))
ma = max(A)
m = (m + ma - 1) // ma
if m == 1:
    print(1)
    exit()
ma = 0
for a in A:
    while a % p == 0:
        a //= p
    ma = max(a, 0)

if ma == 1:
    print(-1)
    exit()
i = 1
ans = 1
while i < m:
    i *= ma
    ans += 1
print(ans)