#include <fstream>
using namespace std;
int G, W, i, E, C;
int v [15000];
ifstream cin ("energii.in");
ofstream cout ("energii.out");
int main()
{
cin >> G >> W;
for(i = 0 ;i < 15000; i ++)
v [i] = 100000;
v [0] = 1;
while (G)
{
cin >> E >> C;
for(i = W-1; i >= 0; i --)
if (i + E <= W)
{
if (v [i+E] > v [i] + C)
    v [i+E] = v [i] + C;
}
else
    if(v [W] > v [i] + C)
        v [W] = v [i]+C;
G --;
}
if(v [W] == 100000)
    cout << "-1";
else
    cout << v [W]-1;
return 0;
}