use proconio::{input, marker::Chars}; fn main() { input!{ s: Chars } let mut cnt = 0; let mut ans = 0usize; let mut l = 0; for i in (0..s.len()).rev(){ if s[i] == '0'{ cnt += 1; l = 0 } else{ l += 1; if l&1==0{ ans += cnt } } } println!("{}",ans); }