#!/bin/bash
a=0
c=0
aim=0

function num() {
	echo $2 # could have used awk, but this works ;p
}

while read line; do
	x=$(num $line)
	if [[ "$line" == "forward"* ]]; then
		a=$((a+x))
		c=$((c+aim*x))
	elif [[ "$line" == "up"* ]]; then
		aim=$((aim-x))
	elif [[ "$line" == "down"* ]]; then
		aim=$((aim+x))
	fi
done

echo $((c*a))