#!/usr/bin/env bash

set -euo pipefail

if [ "$#" -lt 3 ]; then
    cat <<-USAGE
Usage: $0 filename line column
USAGE
    exit 1
fi

fname="$1"
linum="$(("$2"))"
beforelines="$((linum - 1))"
colnum="$3"
beforecols="$((colnum - 1))"

offset=$({
head --quiet --lines "$beforelines" "$fname"
sed -n "${linum}p" "$fname" | awk '{ print substr($0,0,'"$beforecols"') }'
} | wc -c)
echo "$((offset - 1))"