x,y = map(int,input().split())
x = (x*1000)/3600
y = (y*1000)/3600
n = int(input())
an = list(map(int,input().split()))
for i in range(len(an)-1):
    x_time = an[i]/x
    y_dis = x_time*y
    
    if y_dis>an[i+1]:
        print("NO")
        exit()
print("YES")