#include <bits/stdc++.h>
using namespace std;
const int N = 10010;

int n, m, f[N];
int main() {
    // 文件输入
    freopen("2_QiaHaoFill.in", "r", stdin);
    while (cin >> n >> m) {
        memset(f, -0x3f, sizeof(f));
        f[0] = 0;

        for (int i = 1; i <= n; ++i) {
            int v, w;
            cin >> v >> w;

            for (int j = m; j >= v; j--)
                f[j] = max(f[j], f[j - v] + w);
        }
        if (f[m] < 0)
            puts("-1");
        else
            printf("%d\n", f[m]);
    }
    return 0;
}