#include <bits/stdc++.h>

using namespace std;

ifstream fin("energii.in");
ofstream fout("energii.out");
int n, i, j, gr[5002], pr[5002];
int a[2][5002], g;

int main() {
    fin >> n >> g;
    for(i = 1; i <= n; i++) fin >> gr[i] >> pr[i];

    for(j = 1; j <= g; j++) a[0][j] = 5002;
    for(i = 1; i <= n; i++) {
        int p2 = (i & 1);
        int p1 = ((i - 1) & 1);

        for(j = 1; j <= g; j++) {
            a[p2][j] = a[p1][j];

            if(gr[i] <= j) a[p2][j] = min(a[p2][j], pr[i] + a[p1][j - gr[i]]);
        }
    }

    if(a[n & 1][g] == 5002) fout << "-1";
    else fout << a[n & 1][g];

    return 0;
}