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

def f():
  for i in range(0, n-1):
    passed = l[i] / x
    if y * passed > l[i+1]:
      return 'NO'
  
  return 'YES'

print(f())