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") print("i: {}, A[i]: {}, A[i+1]: {}, c: {}, A[i]*c: {}".format(i,A[i],A[i+1],c,A[i]*c)) break else : print("YES")