#include <fstream>
#define D 1003

using namespace std;

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

int sol, e[D], c[D], s, dp[2][5005], G, W;
int main()
{
    f >> G >> W;
    bool ok = 0;
    sol = 1000000000;
    int l = 0;
    for (int i = 1; i <= G; i++){
        f >> e[i] >> c[i];
        s += e[i];
    }
    for (int i = 1; i <= G; i++){
        l = 1 - l;
    for (int j = 0; j <= 5005; j++){
        dp[1 - l][j] = dp[l][j];
        if (c[i] <= j)
            dp[1 - l][j] = max(dp[l][j], dp[l][j - c[i]] + e[i]);
        if (dp[1 - l][j] >= W && j < sol)
            sol = j;
    }
    }
    if (s < W) g << "-1";
        else g << sol;

    return 0;
}