#![allow(non_snake_case)]
#![allow(dead_code)]
#![allow(unused_macros)]
#![allow(unused_imports)]

use std::cmp::*;
use std::collections::HashSet;

macro_rules! input {
    (source = $s:expr, $($r:tt)*) => {
        let mut iter = $s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
    ($($r:tt)*) => {
        let s = {
            use std::io::Read;
            let mut s = String::new();
            std::io::stdin().read_to_string(&mut s).unwrap();
            s
        };
        let mut iter = s.split_whitespace();
        input_inner!{iter, $($r)*}
    };
}

macro_rules! input_inner {
    ($iter:expr) => {};
    ($iter:expr, ) => {};

    ($iter:expr, $var:ident : $t:tt $($r:tt)*) => {
        let $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    };
    ($iter:expr, mut $var:ident : $t:tt $($r:tt)*) => {
        let mut $var = read_value!($iter, $t);
        input_inner!{$iter $($r)*}
    }
}

macro_rules! read_value {
    ($iter:expr, ( $($t:tt),* )) => {
        ( $(read_value!($iter, $t)),* )
    };

    ($iter:expr, [ $t:tt ; $len:expr ]) => {
        (0..$len).map(|_| read_value!($iter, $t)).collect::<Vec<_>>()
    };

    ($iter:expr, chars) => {
        read_value!($iter, String).chars().collect::<Vec<char>>()
    };

    ($iter:expr, usize1) => {
        read_value!($iter, usize) - 1
    };

    ($iter:expr, $t:ty) => {
        $iter.next().unwrap().parse::<$t>().expect("Parse error")
    };
}

macro_rules! chmax {
    ($x:expr, $e:expr) => {
        if $x < $e {
            $x = $e;
        }
    };
}
macro_rules! chmin {
    ($x:expr, $e:expr) => {
        if $x > $e {
            $x = $e;
        }
    };
}

const INF: usize = 1 << 60;

struct Solver {
    D: usize,
    G: usize,
    pc: Vec<(usize, usize)>,
    ans: usize,
}

impl Solver {
    fn dfs(&mut self, i: usize, scores: usize, selected: &mut HashSet<usize>) {
        if i == self.D {
            self.greedy(scores, selected);
            return;
        }
        let (p, c) = self.pc[i];
        selected.insert(i);
        self.dfs(i+1, scores + 100*(i+1)*p + c, selected);
        selected.remove(&i);
        self.dfs(i+1, scores, selected);
    }
    fn greedy(&mut self, mut scores: usize, selected: &mut HashSet<usize>) {
        let mut ans = 0;
        for i in 0..self.D {
            let (p, _) = self.pc[i];
            if selected.contains(&i) {
                ans += p;
            }
        }
        if scores >= self.G {
            chmin!(self.ans, ans);
            //println!("{:?} {}", selected, scores);
            return;
        }
        for i in (0..self.D).rev() {
            let (p, _) = self.pc[i];
            if selected.contains(&i) {
                continue;
            }
            if scores + (100*(i+1)) * p > self.G {
                ans += (self.G - scores + (100*(i+1)) - 1) / (100*(i+1));
                break;
            } else {
                scores += (100*(i+1)) * p;
                ans += p;
            }
        }
        //println!("{:?} {}", selected, scores);
        chmin!(self.ans, ans);
    }
    fn solve(&mut self) {
        self.dfs(0, 0, &mut HashSet::new());
    }
}

fn main() {
    input!{
        D: usize,
        G: usize,
        pc: [(usize, usize); D],
    }
    let mut solver = Solver { D: D, G: G, pc: pc, ans: INF };
    solver.solve();
    println!("{}", solver.ans);
}


Measured memory_bytes: 4352