fn main() {
    let mut n = String::new();
    std::io::stdin().read_line(&mut n).ok();
    let n: usize = n.trim().parse().unwrap();
    const DIVIDER: usize = 1_000_000_007;
    let mut result: usize = 0;
    for _ in 0..n {
        let mut cd = String::new();
        std::io::stdin().read_line(&mut cd).ok();
        let cd: Vec<usize> = cd.trim().split_whitespace().map(|s| s.parse().unwrap()).collect();
        result += (cd[0] + 1) / 2 * cd[1];
        result %= DIVIDER;
    }

    println!("{}", result);
}