Problem 2

#!/bin/bash
# Project Euler - Problem 2

last=0
this=1
total=0

while (($this<4000000))
do 
 f=`expr $this + $last`
 if [ `expr $f % 2` == 0 ] 
 then
 total=`expr $total + $f`
 fi
 last=$this
 this=$f
done
echo $total