import itertools
from collections import deque,defaultdict,Counter
from itertools import accumulate
import bisect
from heapq import heappop,heappush
from fractions import gcd
from copy import deepcopy
import math
import queue
#import numpy as np
#import sympy as syp(素因数分解とか)
Mod = 1000000007
import sys

sys.setrecursionlimit(100000) 
  
def sieve_of_eratosthenes(n):
    if not isinstance(n,int):
        raise TypeError("n is not int")
    if n<2:
        raise ValueError("n is not effective")
    prime = [1]*(n+1)
    for i in range(2,int(math.sqrt(n))+1):
        if prime[i] == 1:
            for j in range(2*i,n+1):
                if j%i == 0:
                    prime[j] = 0
    res = []
    for i in range(2,n+1):
        if prime[i] == 1:
            res.append(i)
    return res

def factorial(i):
    if i == 1:
        return 1
    else:
        return i*factorial(i-1)
 
class UnionFind:
    def __init__(self,n):
        self.parent = [i for i in range(n+1)]
        self.rank = [0 for i in range(n+1)]
    
    def findroot(self,x):
        if x == self.parent[x]:
            return x
        else:
            y = self.parent[x]
            y = self.findroot(self.parent[x])
            return y
    
    def union(self,x,y):
        px = self.findroot(x)
        py = self.findroot(y)
        if px < py:
            self.parent[py] = px
        else:
            self.parent[px] = py
 
    def same_group_or_no(self,x,y):
        return self.findroot(x) == self.findroot(y)


class Dijkstra:
 
    def __init__(self, rote_map, start_point, goal_point=None):
        self.rote_map = rote_map
        self.start_point = start_point
        self.goal_point = goal_point
 
    def execute(self):
        num_of_city = len(self.rote_map)
        dist = [float("inf") for _ in range(num_of_city)]
        prev = [float("inf") for _ in range(num_of_city)]
 
        dist[self.start_point] = 0
        heap_q = []
        heapq.heappush(heap_q, (0, self.start_point))
        route_count = [0 for _ in range(num_of_city)]
        route_count[self.start_point] = 1
        while len(heap_q) != 0:
            prev_cost, src = heapq.heappop(heap_q)
 
            if dist[src] < prev_cost:
                continue
 
            for dest, cost in self.rote_map[src].items():
                if cost != float("inf") and dist[dest] > dist[src] + cost:
                    dist[dest] = dist[src] + cost
                    heapq.heappush(heap_q, (dist[dest], dest))
                    prev[dest] = src
                if dist[dest] == dist[src] + cost:
                    route_count[dest] += route_count[src]
 
        if self.goal_point is not None:
            return self._get_path(self.goal_point, prev)
        else:
            return dist, route_count
 
    def _get_path(self, goal, prev):
        path = [goal]
        dest = goal
 
        while prev[dest] != float("inf"):
            path.append(prev[dest])
            dest = prev[dest]
 
        return list(reversed(path))

        
def main(): #startline--------------------------------------------
    d,g = map(int,input().split())
    pc = [list(map(int,input().split())) for i in range(d)]
    p = [pc[i][0] for i in range(d)]
    c = [pc[i][1] for i in range(d)]
    def dfs(cur,tar):
        if cur == 0:
            return 10**9
        cnt = min(tar//(cur*100),p[cur-1])
        tmp = 100*cur*cnt
        if cnt == p[cur-1]:
            tmp += c[cur-1]
        if tmp < tar:
            cnt += dfs(cur-1,tar-tmp)
        return min(cnt,dfs(cur-1,tar))

    print(dfs(d,g))
if __name__ == "__main__":
    main() #endline===============================================
    

Measured memory_bytes: 5176