#include<iostream>
#include <string>
using namespace std;
int T,N;
int main()
{
	while(cin>>T>>N && T )
	{
		string t_name;
		long long sum=0,scores;
		long long ans=0;
		for(int i=1;i<=T;++i){ cin>>t_name>>scores;sum+=scores;}
		for(ans=0;sum && ans<=N;++ans)if((N-ans)*3+ans*2==sum || ans*2==sum){sum=0;break;}
		cout<<ans<<endl;
	}
	return 0;
}