#include <iostream>
#include <fstream>
using namespace std;
int g,w,egi[100],cgi[100],j,mn,nr=0;
int main()
{
    ifstream f("energii.in");
    ofstream gout("energii.out");
    f>>g;
    f>>w;
    for (int i=1;i<=g;i++)
    {
        f>>egi[i]>>cgi[i];
    }
    for (int i=1;i<=g;i++)
    {
        if (egi[i]==w) {nr++;mn=cgi[i];}
        else
        {
            for (j=i+1;j<=g-1;j++)
            {
                if ((egi[i]+egi[j]==w)and(cgi[i]+cgi[j]<mn)) {nr++;mn=cgi[i]+cgi[j];}
            }
        }
    }
    if (nr!=0) gout<<mn;
    else gout<<-1;
    return 0;
}