LSP violated

BrokenLSP.kt

abstract class Employee {

    abstract fun getSalary(): String

    abstract fun getLineManager(): Employee

}

class SeniorAndroidDeveloper(
    private val leadAndroidDeveloper: LeadAndroidDeveloper
) : Employee() {

    override fun getSalary(): String {
        return "$10000"
    }

    override fun getLineManager(): Employee {
        return leadAndroidDeveloper
    }

}

class LeadAndroidDeveloper(
    private val cto: CTO
) : Employee() {

    override fun getSalary(): String {
        return "$10001"
    }

    override fun getLineManager(): Employee {
        return cto
    }

}

class CTO : Employee() {

    override fun getSalary(): String {
        return "$1000000000000000000"
    }

    override fun getLineManager(): Employee {
        throw RuntimeException("A CTO doesn't have a line manager")
    }
}