X, Y = map(int,input().split())
X /= 3.6
Y /= 3.6

N = int(input())
A = list(map(int,input().split()))

distance = 0
ans = "YES"

for c in range(N-1):
	s = A[c] / X
	distance = (Y - X)*s
	if((A[c+1] - A[c]) < distance):
		ans = "NO"
		break

print(ans)