#include <bits/stdc++.h>

using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
int v[5005];
int main()
{
    int n, g, e, c;
    fin >> n >> g;
    for(int i = 1; i <= g; i++)
        v[i] = INT_MAX - 10005;
    for(int i = 1; i <= n; i++)
    {
        fin >> e >> c;
        for(int j = g; j >= 1; j--)
        {
            if(j > e)
                v[j] = min(v[j], v[j-e] + c);
            else
                v[j] = min(v[j], c);
        }
    }
    if(v[g] != (INT_MAX - 10005))
        fout << v[g];
    else
        fout << "-1";
    return 0;
}