#include <fstream>

using namespace std;

#define N_MAX 1001
#define W_MAX 5001
#define FIN "energii.in"
#define FOUT "energii.out"

int g,w,a[N_MAX],b[N_MAX],i;

int main()
{
	ifstream fin(FIN);
	ofstream fout(FOUT);
	fin >> g >> w;
	for(i = 0; i < g; ++i){
		fin >> a[i] >> b[i];
		if(i == 0){
		    fout << -1;
		    return 0;
		}	
	}
	
	return 0;
}