n, m = map(int, input().split())
ns, ms = n / 3.6, m / 3.6

n = int(input())
A = list(map(int, input().split()))
ans = True
for i in range(n - 1):
    if A[i + 1] < A[i] / ns * ms:
        ans = False
        break
print("YES" if ans else "NO")