from decimal import Decimal

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


c = Decimal(Y) / Decimal(X)

for i in range(N-1) :
    if A[i+1] < A[i] * c :
        print("NO")
        break
else :
    print("YES")