UP 'n' and BACK 'n' functions for terminal

#add to .bashrc

function up( )
{
LIMIT=$1
P="$PWD"
for ((i=1; i <= LIMIT; i++))
do
    P=$P/..
done
cd "$P"
export MPWD=$P
}

function back( )
{
LIMIT=$1
P="$MPWD"
for ((i=1; i <= LIMIT; i++))
do
    P=${P%/..}
done
cd "$P"
export MPWD=$P
}