aoc20_13.sh

bc <<EOF
$(awk -F, '
NR == 1 {
	print "t = " $0
	next
}

{
	j = 0
	for (i = 1; i <= NF; i++) {
		if ($i == "x")
			continue

		print "i[" j "] = " i-1
		print "n[" j "] = " $i
		j++
	}

	print "c = " j
}' input.txt)
for (i = 0; i < c; i++)
	w[i] = n[i] - t%n[i]
w = w[0]
b = n[0]
for (i = 1; i < c; i++)
	if (w[i] < w) {
		w = w[i]
		b = n[i]
	}
w*b
for (i = 0; i < c; i++)
	b[i] = (n[i] - i[i]%n[i]) % n[i]
p = 1
for (i = 0; i < c; i++)
	p *= n[i]
for (i = 0; i < c; i++)
	p[i] = p/n[i]
for (i = 0; i < c; i++) {
	m = p[i]%n[i]
	for (x = 1; m*x % n[i] != 1; x++) {
	}
	x[i] = x
}
for (i = 0; i < c; i++)
	s += b[i]*p[i]*x[i]
s%p
EOF