L, R, M, K = list(map(int, input().split()))

import math
# if L*K <= M <= R*K:
if math.floor(R * K / M) - math.floor(L * K /M) >= 1 or R == 0 or L == 0 (R == L and (R * K) % M == 0) or K == 0:
    print('Yes')
else:
    print('No')