l, r, m, k = map(int, input().split())

if l == 0:
    print("Yes")
    exit()

if k == 0:
    print("Yes")
    exit()

if m == 1:
    print("Yes")
    exit()

if l == r:
    if (l * k) % m == 0:
        print("Yes")
    else:
        print("No")
    exit()

    
mod_l = l % m
mod_r = r % m

if mod_l > mod_r:
    print("Yes")
    exit()

width = mod_r - mod_l
sum_w = 1 + width * k

if sum_w >= m:
    print("Yes")
    exit()

l = (mod_l * k) % m
if l + (sum_w - 1) >= m:
    print("Yes")
else:
    print("No")