X=[float(i) for i in input().split()]
N=int(input())
A=[int(i) for i in input().split()]
for i in range(2):
  #  X[i]=X[i]*18/5
     X[i]=X[i]
i= 1
e=0
while e==0 and i<N:
#    T=A[i]/X[1]
    T=A[i]/X[1]
# K=X[0]*T
    K=X[0]*T
    if K<A[i-1]:
        e=1
        print("NO")
    i+=1
if e==0:
    print("YES")