X, Y = map(int,input().split())
N = int(input())
A = list(map(int,input().split()))
P = X / 3.6
Q = Y / 3.6
DIS = 0
ANS = "YES"
for I in range(N - 1):
	S = A[I] / X
	DIS = (Y - X) * S
	if (round((A[I + 1] - A[I]), 6) < round(DIS, 6)):
		ANS = "NO"
		break
print(ANS)