#include <bits/stdc++.h>
#define nmax 10005

using namespace std;

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

int dp[nmax / 2][nmax], n, g, gr[nmax], p[nmax], pmax;

int main()
{
    fin >> n >> g;
    for (int i = 1; i <= n; i++)
    {
        fin >> gr[i] >> p[i];
    }
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= g; j++)
            dp[1][j] = dp[2][j];
        for (int j = 1; j <= g; j++)
        {
            if ((j - gr[i]) >= 0)
            {
                dp[2][j] = max(dp[1][j], dp[1][j - gr[i]] + p[i]);
            }
            else dp[2][j] = dp[1][j];
        }
    }
    if (dp[2][g] < g) dp[2][g] = -1;
    fout << dp[2][g];
    return 0;
}