#include <bits/stdc++.h>
using namespace std;
const int N = 10010;
int n, m, f[N][N];

int main() {
    // 文件输入
    freopen("2_QiaHaoFill.in", "r", stdin);
    while (cin >> n >> m) {
        memset(f, -0x3f, sizeof(f));             // 其它位置全部初始化为-INF
        for (int i = 0; i < N; i++) f[i][0] = 0; // 第一列初始化为0

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

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