use std::cmp::Reverse;

const INF: usize = 1usize << 60;

fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: usize = n.trim().parse().unwrap();
    let mut items = (0..n).map(|_| {
            let mut temp = String::new();
            std::io::stdin().read_line(&mut temp).ok();
            let temp: Vec<usize> = temp.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
            (temp[0], temp[1])
        })
        .collect::<Vec<_>>();

    items.sort_by_key(|&(_, b)| Reverse(b));
    let limit = n / 3;
    let mut dp = vec![vec![INF; limit+1]; n+1];
    dp[0][0] = 0;
    for i in 0..n {
        let (a, b) = items[i];
        for j in 0..=limit {
            if dp[i][j] == INF { continue; }
            dp[i+1][j] = dp[i+1][j].min(dp[i][j] + a + (i - j) * b);
            if j+1 <= limit {
                dp[i+1][j+1] = dp[i+1][j+1].min(dp[i][j]);
            }
        }
    }
    println!("{}", dp[n][limit]);
}