timestamp=$(shell date +%Y-%m-%d_%H:%M)

all: td1

td1: td1.tex
	@latexmk -pdf td1.tex
	@if ! cmp --silent build/td1.pdf td1_*.pdf; then \
		touch td1_tmp.pdf; \
		rm td1*.pdf; \
		cp build/td1.pdf td1_${timestamp}.pdf; \
		echo "Updated"; \
	fi

clean:
	@rm -rf build 2>/dev/null