#include <iostream>
#include <fstream>
using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
//G - numarul de generatoare
//W - cantitatea de energie necesara
//EG - cantitatea de energie produsa de generator
//CG - costul necesar producerii
//d[i][j] - ENERGIA MAXIMA CARE POATE FI PRODUSA DE GENERATOARELE PANA LA I FOLOSIND J LEI
int G, W, EG[1005], CG[1005];
int d[1005][5005];
void citire() {
    fin >> G >> W;
    for (int i=1; i<=G; ++i) {
        fin >> EG[i] >> CG[i];
    }
}
int main()
{
    citire();
    int costmax=0;
    bool OK=false;
    int costnecesar=0;
    for (int i=1 ;i<=G; ++i) {
        costmax=costmax+CG[i];
    }
    for (int i=1; i<=G; ++i) {
        for (int j=0; j<=CG[i]-1; ++j) {
            d[i][j]=d[i-1][j];
        }
        for (int j=CG[i]; j<=costmax; ++j) {
            d[i][j]=max(EG[i]+d[i-1][j-CG[i]], d[i-1][j]);
        }
    }
    for (int i=1; i<=G; ++i) {
        for (int j=0; j<=costmax; ++j) {
            if (d[i][j]>=W) {
                costnecesar=j;
                OK=true;
                break;
            }
        }
    }
    if (OK==true) {
        fout << costnecesar;
    }
    else {
        fout << -1;
    }
    return 0;
}