# 両辺に b^2 d^2 をかける解法

import sys

read = sys.stdin.buffer.read
readline = sys.stdin.buffer.readline
readlines = sys.stdin.buffer.readlines

a, b, c, d = map(int, read().split())

LHS = a * d * b * d
RHS = b * c * b * d

print('Yes' if LHS < RHS else 'No')