x,y = map(int, raw_input().split())
n = int(raw_input())
l = map(int, raw_input().split())
x /= 3.6
y /= 3.6
for i in range(n-1):
    t = l[i] / x
    p = y * t
    if p > l[i+1]:
        print 'NO'
        break;
else:
    print 'YES'