[CentOS] how to install yum by apt

Hi all!
  Becaule i heard that the apt was great,i wanted to try it.And when i tried to update my system,the yum faid,i installed the apt which came from dag repo by yum. After that i did:sudo apt-get update and sudo apt-get upgrade.There are some problem and i did as apt suggested:sudo apt-get --fix-broken install.Then apt said should remove 11 softwares insclude yum.I thougt even i removed the yum,i could installed it by apt again,so i removed them.
  After that i found i could not use apt smooth,there were many problem,so i want to install yum again.But apt couldn't find the yum package. In /etc/apt/sources.list.d,there are two lists:rpmforge.list and os.list.
   rpmforge.list:
# Name: RPMforge RPM Repository for Red Hat Enterprise 5 - dag
# URL: http://rpmforge.net/
#rpm http://apt.sw.be redhat/el$(VERSION)/en/$(ARCH) dag
repomd http://apt.sw.be redhat/el$(VERSION)/en/$(ARCH)/dag
repomd http://apt.sw.be redhat/el$(VERSION)/en/$(ARCH)/dag

os.list:
# Name: Operating system and updates

### Red Hat Enterprise Linux
#repomd http://mirror.centos.org centos/$(VERSION)/os/$(ARCH)
#repomd http://mirror.centos.org centos/$(VERSION)/updates/$(ARCH)
#repomd http://mirror.centos.org centos/$(VERSION)/extras/$(ARCH)
#repomd http://mirror.centos.org centos/$(VERSION)/fasttrack/$(ARCH)
#repomd http://mrepo rhel$(VERSION)s-$(ARCH)/RPMS.os
#repomd http://mrepo rhel$(VERSION)s-$(ARCH)/RPMS.updates
#rpm http://mrepo rhel$(VERSION)s-$(ARCH) os updates

### Fedora Core Linux
#repomd http://ayo.freshrpms.net fedora/linux/$(VERSION)/$(ARCH)/core
#repomd http://ayo.freshrpms.net fedora/linux/$(VERSION)/$(ARCH)/updates
#rpm http://ayo.freshrpms.net fedora/linux/$(VERSION)/$(ARCH) core updates

### Red Hat Linux
#repomd http://ayo.freshrpms.net redhat/$(VERSION)/$(ARCH)/os
#repomd http://ayo.freshrpms.net redhat/$(VERSION)/$(ARCH)/updates
#rpm http://ayo.freshrpms.net redhat/$(VERSION)/$(ARCH) os updates

What should i do?
 
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