18.02 1

use std::{
    fmt::Debug,
    fs::File,
    io,
    io::Read,
    iter::FromIterator,
    num::ParseIntError,
    str::{FromStr, SplitWhitespace},
};

#[inline]
#[allow(dead_code)]
fn input() -> String {
    let mut input = String::new();
    unsafe {
        io::stdin().read_line(&mut input).unwrap_unchecked();
    }
    input
}

#[inline]
#[allow(dead_code)]
fn input_parse<T: FromStr<Err = ParseIntError> + Debug>() -> T {
    let mut input = String::new();
    unsafe {
        io::stdin().read_line(&mut input).unwrap_unchecked();
        input.trim().parse().unwrap_unchecked()
    }
}

#[inline]
#[allow(dead_code)]
fn input_container<T, C>() -> C
where
    T: FromStr<Err = ParseIntError> + Debug,
    C: FromIterator<T>,
{
    let mut input = String::new();
    unsafe {
        io::stdin().read_line(&mut input).unwrap_unchecked();
    }

    input
        .split_whitespace()
        .map(|x| unsafe { x.parse::<T>().unwrap_unchecked() })
        .collect::<C>()
}

#[inline]
#[allow(dead_code)]
fn input_pair<F, S>() -> (F, S)
where
    F: FromStr<Err = ParseIntError> + Debug,
    S: FromStr<Err = ParseIntError> + Debug,
{
    let mut input = String::new();
    unsafe {
        io::stdin().read_line(&mut input).unwrap_unchecked();
    }

    let mut input = input.split_whitespace();

    unsafe {
        (
            input.next().unwrap().parse().unwrap_unchecked(),
            input.next().unwrap().parse().unwrap_unchecked(),
        )
    }
}

#[inline]
#[allow(dead_code)]
fn input_it(mut input: &mut String) -> SplitWhitespace<'_> {
    unsafe {
        io::stdin().read_line(&mut input).unwrap_unchecked();
    }
    input.split_whitespace()
}

trait IterExt: std::iter::ExactSizeIterator {
    #[inline]
    fn filter_indexed(&mut self, mut f: impl FnMut(&Self::Item, usize) -> bool) -> Vec<Self::Item> {
        let mut filter = Vec::with_capacity(self.len());

        for i in 0..self.len() {
            let nxt = unsafe { self.next().unwrap_unchecked() };

            if f(&nxt, i) {
                filter.push(nxt)
            }
        }

        filter.shrink_to_fit();
        filter
    }
}

impl<T> IterExt for std::slice::Iter<'_, T> {}

fn main() {
    let nums = {
        let mut input = String::new();

        unsafe {
            File::open("kek.txt")
                .unwrap_unchecked()
                .read_to_string(&mut input)
                .unwrap_unchecked();
        }

        input
    }
    .trim()
    .split('\n')
    .skip(1)
    .map(|i| unsafe {
        let mut it = i.split(" ").map(|x| x.parse::<u32>().unwrap_unchecked());
        (it.next().unwrap_unchecked(), it.next().unwrap_unchecked())
    })
    .collect::<Vec<_>>();

    let ans = nums
        .iter()
        .fold(0, |acc, (f, s)| acc + std::cmp::min(*f, *s));

    println!(
        "{}",
        ans + match ans % 3 {
            0 => unsafe {
                nums.into_iter()
                    .map(|(f, s)| f.abs_diff(s))
                    .filter(|x| *x % 3 != 0)
                    .min()
                    .unwrap_unchecked()
            },

            _ => 0,
        }
    )
}