pub trait ChangeBest { fn chmin(&mut self, v: Self) -> bool; fn chmax(&mut self, v: Self) -> bool; } impl ChangeBest for T where T: PartialOrd, { fn chmin(&mut self, v: T) -> bool { if *self > v { *self = v; true } else { false } } fn chmax(&mut self, v: T) -> bool { if *self < v { *self = v; true } else { false } } } #[allow(unused_macros)] macro_rules! mat { ($e:expr; $d:expr) => { vec![$e; $d] }; ($e:expr; $d:expr $(; $ds:expr)+) => { vec![mat![$e $(; $ds)*]; $d] }; } #[allow(unused_macros)] macro_rules! input { (source = $s:expr, $($r:tt)*) => { let mut iter = $s.split_whitespace(); let mut next = || { iter.next().unwrap() }; input_inner!{next, $($r)*} }; ($($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)*} }; } #[allow(unused_macros)] 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)*} }; } #[allow(unused_macros)] macro_rules! read_value { ($next:expr, ( $($t:tt),* )) => { ( $(read_value!($next, $t)),* ) }; ($next:expr, [ $t:tt ; $len:expr ]) => { (0..$len).map(|_| read_value!($next, $t)).collect::>() }; ($next:expr, chars) => { read_value!($next, String).chars().collect::>() }; ($next:expr, usize1) => { read_value!($next, usize) - 1 }; ($next:expr, $t:ty) => { $next().parse::<$t>().expect("Parse error") }; } fn main() { input! { s: String }; let len = s.chars().filter(|c| *c == 'a').count(); let t = (0..len).map(|_| 'a').collect::(); println!("{}", t); }