Problem:
Score : 300 points

Problem Statement

A programming competition site AtCode provides algorithmic problems.
Each problem is allocated a score based on its difficulty.
Currently, for each integer i between 1 and D (inclusive), there are p_i problems with a score of 100i points.
These p_1 + … + p_D problems are all of the problems available on AtCode.

A user of AtCode has a value called total score.
The total score of a user is the sum of the following two elements:

Base score: the sum of the scores of all problems solved by the user.

Perfect bonuses: when a user solves all problems with a score of 100i points, he/she earns the perfect bonus of c_i points, aside from the base score (1 ≤ i ≤ D).

Takahashi, who is the new user of AtCode, has not solved any problem.
His objective is to have a total score of G or more points.
At least how many problems does he need to solve for this objective?

Constraints

1 ≤ D ≤ 10

1 ≤ p_i ≤ 100

100 ≤ c_i ≤ 10^6

100 ≤ G

All values in input are integers.

c_i and G are all multiples of 100.

It is possible to have a total score of G or more points.

Input

Input is given from Standard Input in the following format:

D G
p_1 c_1
:
p_D c_D

Output

Print the minimum number of problems that needs to be solved in order to have a total score of G or more points. Note that this objective is always achievable (see Constraints).

Sample Input 1

2 700
3 500
5 800

Sample Output 1

3

In this case, there are three problems each with 100 points and five problems each with 200 points. The perfect bonus for solving all the 100-point problems is 500 points, and the perfect bonus for solving all the 200-point problems is 800 points. Takahashi's objective is to have a total score of 700 points or more.

One way to achieve this objective is to solve four 200-point problems and earn a base score of 800 points. However, if we solve three 100-point problems, we can earn the perfect bonus of 500 points in addition to the base score of 300 points, for a total score of 800 points, and we can achieve the objective with fewer problems.

Sample Input 2

2 2000
3 500
5 800

Sample Output 2

7

This case is similar to Sample Input 1, but the Takahashi's objective this time is 2000 points or more. In this case, we inevitably need to solve all five 200-point problems, and by solving two 100-point problems additionally we have the total score of 2000 points.

Sample Input 3

2 400
3 500
5 800

Sample Output 3

2

This case is again similar to Sample Input 1, but the Takahashi's objective this time is 400 points or more. In this case, we only need to solve two 200-point problems to achieve the objective.

Sample Input 4

5 25000
20 1000
40 1000
50 1000
30 1000
1 1000

Sample Output 4

66

There is only one 500-point problem, but the perfect bonus can be earned even in such a case.

Solution in Rust (1.15.1) (judge verdict: Accepted)

#[allow(dead_code)]
fn main() {
    let buf = io::read_string();
    let mut sc = io::Scanner::new(&buf);
    let d: usize = sc.read();
    let g: usize = sc.read();
    let p: Vec<(usize, usize)> = (0..d).map(|_| (sc.read(), sc.read())).collect();
    let mut res = 10000000000;
    for b in 0..(1 << d) {
        let mut sum = 0;
        let mut num = 0;
        let mut m = 0;
        for i in 0..d {
            if b >> i & 1 == 1 {
                sum += 100 * (i + 1) * p[i].0 + p[i].1;
                num += p[i].0;
            } else {
                m = i;
            }
        }
        if sum < g {
            let s = 100 * (m + 1);
            let c = (g - sum + s - 1) / s;
            if c >= p[m].0 {
                continue;
            }
            num += c;
        }
        res = std::cmp::min(res, num);
    }
    println!("{}", res);
}
#[allow(dead_code)]
mod io {
    use std;
    use std::io::Read;
    use std::str::{FromStr, SplitWhitespace};
    pub struct Scanner<'a> {
        pub iter: SplitWhitespace<'a>,
    }
    impl<'a> Scanner<'a> {
        pub fn new(s: &'a str) -> Scanner<'a> {
            Scanner {
                iter: s.split_whitespace(),
            }
        }
        pub fn read<T: FromStr>(&mut self) -> T {
            self.iter
                .next()
                .unwrap()
                .parse()
                .ok()
                .expect("parsing failed")
        }
        pub fn read_vec<T: FromStr>(&mut self, n: usize) -> Vec<T> {
            (0..n).map(|_| self.read()).collect()
        }
    }
    pub fn read_string() -> String {
        let mut s = String::new();
        std::io::stdin().read_to_string(&mut s).unwrap();
        s
    }
}