X, Y = (int(i)*1000 for i in input().split())
N = int(input())
A = [int(i)*3600 for i in input().split()]

flag = True
for i in range(N-1):
    #print("{0},{1}".format(A[i+1]/Y, A[i]/X))
    if A[i+1]/Y < A[i]/X:
        flag = False
        break
print("YES" if flag else "NO")