X,Y = map(int,input().split())
N = int(input())
As = [int(x) for x in input().split()]
x = X / 3600 * 1000
y = Y / 3600 * 1000

for i in range(N - 1):
    y_pos=As[i]/x*y
    if y_pos > As[i+1]:
        print("NO")
        break
else:
    print("YES")