pub fn main() {
    let v = vec![
        (1, 31),
        (2, 28),
        (3, 31),
        (4, 30),
        (5, 31),
        (6, 30),
        (7, 31),
        (8, 31),
        (9, 30),
        (10, 31),
        (11, 30),
        (12, 31),
    ];
    let all_date: Vec<(usize, usize)> = v.iter()
        .flat_map(|&(m, d)| (1..d).map(move |x| (m, x)))
        .collect();
    let sum_digit = |x| (x / 10) + (x % 10);

    let answer = all_date.into_iter().filter(|&(m, d)| m == sum_digit(d)).count();
    println!("{}", answer);
}