import sys
read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

import numpy as np

X,Y = map(int,readline().split())
N = int(readline())
A = np.array(read().split(),np.int64)

T1 = A / X
T2 = A / Y

eps = 10**(-5)
condition = np.all(T1[:-1] < T2[1:]+eps)

answer = 'YES' if condition else 'NO'
print(answer)