#include <iostream>
#include <fstream>
#define NMAX 1003
#define GMAX 5001
using namespace std;

ifstream in("energii.in");
ofstream out("energii.out");

int n,c,g[NMAX],p[NMAX],d[NMAX][GMAX];

int main()
{
    in >> n >> c;

    for(int i=1;i<=n;i++)
    {
       in >> g[i] >> p[i];
    }

    for(int i=1;i<=n;i++)
    {
        for(int k=1;k<=c;k++)
        {
            d[i][k] = d[i-1][k];
            if(k-g[i]>=0 && d[i][k]<d[i-1][k-g[i]] + p[i])
            {
                d[i][k] = d[i-1][k-g[i]] + p[i];
            }
        }
    }
    if(c<=d[n][c]) out << d[n][c];
    else out << -1;


    return 0;
}