Infrastructure Software

I changed the shell of my root user directory to
from /sbin/sh to /sbin/ksh

however, this machine does not have the binary
for ksh in that directory position but in
/bin/ksh

Now every time i want to loggin as a root user, it denies me access with an error;
su: No shell

Now i can not log into my machine with a root password since it can not find the shell.

I have acces as other normal user of the machine and also have the root password.

this is what i tryed>

su - root -c /bin/ksh

but it still does not read a shell.

Any suggestion to fix this problems will be very much appreciated.