#include <iostream>
#include <fstream>
#define E 20003
#define dim 1003

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

int n, i, j, w, v[E], x, y, e, c;

int main () {
    
    fin >> n >> w;
    for (i = 1; i <= w; i++)
        v[i] = n*n;
    
    for (i = 1; i <= n; i++)
    {
        fin >> e >> c;
        for (j = w; j >= 0; j--)
        {
            if (j <= e)
                v[j] = min(v[j], c);
            else if (v[j-e] != n*n)
                v[j] = min(v[j], v[j-e]+c);
        }
    }
    
    if (v[w] != n*n)
        fout << v[w] << "\n";
    else fout << -1 << "\n";
}