fn main
[
	var input := read_lazy(h[0]);
	var fs := true;
	var id := 0;
	var ids := empty(int);
	while len_greater_than(input, 0), input[0] >= '0', input[0] <= '9' do [
		var num := input[0] - '0';
		if fs then [
			for i := 0 to num do
				ids +<= id;
			id += 1;
		] else [
			ids += fill(-1, num);
		]
		fs := not fs;
		input := input[1 .. ];
	]
	var dest := 0;
	var src := len(ids) - 1;
	while dest < src do [
		if ids[dest] >= 0 then [
			dest += 1;
			continue;
		]
		if ids[src] < 0 then [
			src -= 1;
			continue;
		]
		ids[dest], ids[src] := ids[src], -1;
	]
	var sum := 0;
	for i := 0 to dest do
		sum += i * ids[i];
	write(h[1], ntos(sum) + nl);
	xeval ids;
]