x, y = map(int, input().split())
n = int(input())
a = list(map(int, input().split()))
x *= 1000
y *= 1000
x /= 3600
y /= 3600

flag = True
for i in range(n - 1):
    if a[i] * y > a[i + 1] * x:
        flag = False

if flag:
    print("YES")
else:
    print("NO")