#!/bin/bash

# Find valid calls of mul
valid_mull_calls=$(cat input.txt | grep 'mul([[:digit:]]\+,[[:digit:]]\+)' -o)

# Remove everything except the numbers with delimiting commas.
mul_args_only=$(echo "$valid_mull_calls" | sed 's/mul(//g' | sed 's/)//g')

mul () {
    # Takes a string of number1,number2 and multiplies them.
    local multiplicand=$(echo $1 | cut -d , -f 1)
    local multiplier=$(echo $1 | cut -d , -f 2)
    echo $((multiplicand * multiplier))

}

total=0
# Loop over multiplicand,multiplier pairs and aggregate the sum of their products.
for args in $(  echo $mul_args_only | xargs  ); do
    product=$(mul $args)
    total=$((total + product))
done

echo $total