#include<iostream>
#include<cstdio>
#include<cstring>

using namespace std;

int D;
unsigned long long G,v[1111],w[1111],sum,cnt,minn=1000000000000ull;
bool check[1111];

int main(){
	cin>>D>>G;
	for(int i=0;i<D;++i)cin>>v[i]>>w[i];
	for(int i=0;i<1<<D;++i){
		cnt=sum=0ll;
		memset(check,false,sizeof(check));
		for(int j=0;j<D;++j)if(i&(1<<j))sum+=v[j]*(j+1ull)*100ull+w[j],cnt+=v[j],check[j]=true;
		if(sum>=G)goto endd;
		for(int j=D-1;~j;--j){
			if(check[j])continue;
			for(int k=1;k<=v[j];++k){
				sum+=(j+1ull)*100ull;
				++cnt;
				if(sum>=G)goto endd;
			}
		}
		endd:
		minn=min(minn,cnt);
	}
	cout<<minn;
}