x_h,y_h = map(int, input().split())
n_traffics = int(input())
traffics = list(map(int, input().split()))
traffics.append(10000000000000000000) # 番兵

# 秒速に変更とkm => m
x_s = x_h * 1000
y_s = y_h * 1000

for i in range(n_traffics):
    time = traffics[i] / x_s
    if time * y_s > traffics[i + 1]:
        print("NO")
        exit(0)
print("YES")