"Manifest merger failed with multiple errors" hata ...

Bu benim AndroidManifest.xml kodum :

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.mkmakerblog.makerchat">

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".anaEkran">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".RegisterActivity"
            android:parentActivityName=".MainActivity" />
        <activity
            android:name=".LoginActivity"
            android:parentActivityName=".MainActivity" />
        <activity
            android:name=".MainActivity"
            android:parentActivityName=".RegisterActivity"/>
        <activity
            android:name=".MainActivity"
            android:parentActivityName=".LoginActivity"/>
<activity
    android:name=".MainActivity">
</activity>

    </application>
</manifest>

Merged manifest kısmındaki hata görünümü de bu:

Merging Errors: Error: Element activity#com.mkmakerblog.makerchat.MainActivity at AndroidManifest.xml:28:9-30:58 duplicated with element declared at AndroidManifest.xml:25:9-27:61 app main manifest (this file), line 27 Error: Element activity#com.mkmakerblog.makerchat.MainActivity at AndroidManifest.xml:31:1-33:12 duplicated with element declared at AndroidManifest.xml:28:9-30:58 app main manifest (this file), line 30 Error: Validation failed, exiting app main manifest (this file)

Tam çözemedim lütfen yardım eder misiniz.