from bisect import bisect_left

x, y = map(int, input().split())
n = int(input())
A = list(map(int, input().split()))

for i in range(n):
    t = A[i] / x
    d = t * y
    idx = bisect_left(A, d)
    if idx - i > 1:
        print("NO")
        exit()
print("YES")