use proconio::input;

fn main() {
    input! {
        s: String,
    }

    let mut removed_length = 0_usize;
    let mut lt_cnt = 0_usize;
    let mut stack = vec![];
    for c in s.chars() {
        match c {
            '<' => {
                lt_cnt += 1;
                stack.push('<');
            }
            '=' => {
                stack.push('=');
            }
            '>' => {
                if lt_cnt == 0 || stack.last() != Some(&'=') {
                    lt_cnt = 0;
                    stack.push('>');
                } else {
                    removed_length += 1;
                    while let Some(prev_c) = stack.pop() {
                        removed_length += 1;

                        if prev_c == '<' {
                            break;
                        }
                    }
                }
            }
            _ => panic!(),
        }
    }

    println!("{}", s.len() - removed_length);
}