Router with RJ11 input convert to RJ45 input

Router with RJ11 input convert to RJ45 input
I have Aztech 4-port ADSL2/2+ Wireless-G Modem Router which is given to me by my friend. The problem is, I have internet connection where my ISP cable uses RJ45 while the router DSL input is RJ11. How could I connect the RJ45 connector to RJ11 socket? Anyone here knows how to convert from RJ45 connector to RJ11? Or any adapter needed for this conversion. Thanks!
