#define _CRT_SECURE_NO_WARNINGS
#pragma GCC target("avx")
#pragma GCC optimize("O3")
#include <algorithm>
#include <bitset>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <complex>
#include <ctime>
#include <deque>
#include <fstream>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <memory>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <string.h>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>
#define rep(i,n) for(int i=0;i<(lint)(n);i++)
#define REP(i,n) for(int i=1;i<=(lint)(n);i++)
#define all(V) V.begin(),V.end()
#define stackReplaceBegin(size)\
	void* p=malloc(size);\
	esp_new=(lint)p+size-1;\
	void * stack_extend_memory_ = malloc(size);\
	void * stack_extend_origin_memory_;\
	char * stack_extend_dummy_memory_ = (char*)alloca((1+(int)(((long long)stack_extend_memory_)&127))*16);\
	*stack_extend_dummy_memory_ = 0;\
	asm volatile("mov %%rsp, %%rbx\nmov %%rax, %%rsp":"=b"(stack_extend_origin_memory_):"a"((char*)stack_extend_memory_+(size)-1024));
typedef long long lint;
typedef unsigned long long ulint;
typedef std::pair<int, int> P;
constexpr int INF = INT_MAX/2;
constexpr lint LINF = LLONG_MAX/2;
constexpr double eps = DBL_EPSILON;
constexpr double PI = 3.141592653589793238462643383279;
lint esp_new;
template<class T>
class prique :public std::priority_queue<T, std::vector<T>, std::greater<T>> {};
template <class T, class U>
inline bool chmax(T& lhs, const U& rhs) {
	if (lhs < rhs) {
		lhs = rhs;
		return 1;
	}
	return 0;
}
template <class T, class U>
inline bool chmin(T& lhs, const U& rhs) {
	if (lhs > rhs) {
		lhs = rhs;
		return 1;
	}
	return 0;
}
inline lint gcd(lint a, lint b) {
	while (b) {
		lint c = a;
		a = b; b = c % b;
	}
	return a;
}
inline lint lcm(lint a, lint b) {
	return a / gcd(a, b) * b;
}
bool isprime(lint n) {
	if (n == 1)return false;
	for (int i = 2; i * i <= n; i++) {
		if (n % i == 0)return false;
	}
	return true;
}
template<typename T>
T mypow(T a, unsigned int b) {
	T res(1),now(a);
	while(b){
		if(b&1)res*=now;
		b>>=1;
		now*=now;
	}
	return res;
}
template<typename T>
void printArray(std::vector<T>& vec) {
	rep(i, (int)vec.size() - 1)std::cout << vec[i] << " ";
	if(!vec.empty())std::cout << vec.back() << std::endl;
}
template<typename T>
void printArray(T l, T r) {
	T rprev = r;
	rprev--;
	for (T i = l; i != rprev; i++) {
		std::cout << *i << " ";
	}
	std::cout << *rprev << std::endl;
}
int m;
int main(){
	lint sum=0,digits=0;
	std::cin>>m;
	rep(i,m){
		lint d,c;
		std::cin>>d>>c;
		sum+=d*c;
		digits+=c;
	}
	std::cout<<digits-1+(sum-1)/9<<std::endl;
	return 0;
}

#include <bits/stdc++.h>
#define rep(i, n) for (int i{ 0 }; i < n; ++i)

using namespace std;

int main() {
    int d, g;
    cin >> d >> g;
    vector<int> ps(d);
    vector<int> cs(d);

    rep(i, d) cin >> ps[i] >> cs[i];
    // for(auto p :cs) cout <<p;

    int min_cnt{ INT_MAX };
    rep(i, 1 << d) {
        int cnt{ 0 };
        int score{ 0 };
        rep(j, d) if (i >> j & 1) {
            score += ps.at(j) * 100 * (j + 1) + cs.at(j);
            cnt += ps.at(j);
        }
        // cout << "i: " << i << "cnt: " << cnt << "score: " << score << endl;

        for (int j = d - 1; j >= 0; j--) {
            if (score >= g) continue;
            if (i >> j & 1) continue;
            int q = min((int)((g - score) / ((j + 1) * 100)), ps.at(j));
            score += q * 100 * (j + 1);
            cnt += q;
            // cout << "q: " << q << "cnt: " << cnt << "score: " << score << endl;
        }
        // cout << "i: " << i << "cnt: " << cnt << "score: " << score << endl;

        if (score >= g) min_cnt = min(min_cnt, cnt);
    }

    cout << min_cnt << endl;
}
