use std::mem; fn main(){ let mut sc = Scanner::new(); while let Ok(s) = sc.wrapped::() { let mut s = s; let mut a = sc.next(); let mut b = sc.next(); if a == b { s.remove(a); } else { if a > b { mem::swap(&mut a, &mut b); } s.remove(b); s.remove(a); } println!("{}", s); } } #[allow(dead_code)] struct Scanner { token_buffer : Vec, index : usize, } #[allow(dead_code)] impl Scanner { fn new() -> Scanner { Scanner { token_buffer: vec![], index: 0 } } fn wrapped(&mut self) -> Result where T: std::str::FromStr { let s = try!(self.fetch_token()); let t = try!(s.parse::().map_err(|_| "Parse error")); Ok(t) } fn next(&mut self) -> T where T: std::str::FromStr { self.wrapped::().unwrap() } fn fetch_token(&mut self) -> Result<&String,&str> { while self.index >= self.token_buffer.len() { let mut st = String::new(); while st.trim() == "" { match std::io::stdin().read_line(&mut st) { Ok(l) if l > 0 => continue, Ok(_) => return Err("End of file"), Err(_) => return Err("Failed to read line"), } } self.token_buffer = st.split_whitespace() .map(|x| x.to_string()) .collect(); self.index = 0; } self.index += 1; Ok(&self.token_buffer[self.index - 1]) } }