#include <fstream>
#define INF 50000010
using namespace std;
int D[5010];
int C[1010], E[1010];
int n, G, i, j, k;
37
prof. Marius Nicoli
int main () {
ifstream fin("energii.in");
ofstream fout("energii.out");
fin>>n>>G;
for (i=1;i<=n;i++) {
fin>>E[i]>>C[i];
}
for (i=1;i<=G;i++)
D[i] = INF;
for (i=1;i<=n;i++) {
for (j=G-1;j>=0;j--)
if (D[j] != INF) {
k = j+E[i];
if (k > G)
k = G;
if (D[k] > D[j] + C[i])
D[k] = D[j] + C[i];
}
}
if (D[G] == INF)
fout<<-1;
else
fout<<D[G];
return 0;
}