// https://qiita.com/tanakh/items/0ba42c7ca36cd29d0ac8 macro_rules! input { ($($r:tt)*) => { let stdin = std::io::stdin(); let mut bytes = std::io::Read::bytes(std::io::BufReader::new(stdin.lock())); let mut next = move || -> String{ bytes.by_ref().map(|r|r.unwrap() as char) .skip_while(|c|c.is_whitespace()) .take_while(|c|!c.is_whitespace()) .collect() }; input_inner!{next, $($r)*} }; } macro_rules! input_inner { ($next:expr) => {}; ($next:expr,) => {}; ($next:expr, $var:ident : $t:tt $($r:tt)*) => { let $var = read_value!($next, $t); input_inner!{$next $($r)*} }; } macro_rules! read_value { ($next:expr, [ $t:tt ; $len:expr ]) => { (0..$len).map(|_| read_value!($next, $t)).collect::>() }; ($next:expr, $t:ty) => ($next().parse::<$t>().expect("Parse error")); } /// Generates an Iterator over subsets of univ, in the descending order. /// Verified by: http://judge.u-aizu.ac.jp/onlinejudge/review.jsp?rid=3050308 struct SubsetIter { bits: Option, univ: usize } impl Iterator for SubsetIter { type Item = usize; fn next(&mut self) -> Option { match self.bits { None => None, Some(bits) => { let ans = bits; self.bits = if bits == 0 { None } else { Some((bits - 1) & self.univ) }; Some(ans) } } } } fn subsets(univ: usize) -> SubsetIter { SubsetIter { bits: Some(univ), univ: univ } } fn main() { input! { n: usize, w: i64, a: [i64; n], } let mut ans = 0; for bits in 1..1 << n { let mut ok = false; for sub in subsets(bits) { let mut s = 0; for i in 0..n { if (sub & 1 << i) != 0 { s += a[i] / 2; } else if (bits & 1 << i) != 0 { s += a[i]; } } if s == w { ok = true; } } if ok { ans += 1; } } println!("{}", ans); }