import sys


def input(): return sys.stdin.readline().rstrip('\n')


def main():
    l, r, m, k = map(int, input().split())
    return 'Yes' if (l * k - 1) // m != r * k // m else 'No'


if __name__ == '__main__':
    ret = main()
    if ret is not None:
        print(ret)