TEXT=`cat`
set -- $TEXT
a=$1
b=$2
c=$3
hi=1000000000000000000
lo=0

while [ $((hi-lo)) -gt 1 ]
do
    mid=$(((hi+lo)/2))
    if [ $((mid/a*b+(mid-mid/a))) -ge $c ] ; then
        hi=$mid
    else
        lo=$mid
    fi
done
echo $hi