#include <fstream>
#include <cstring>
#define INF 0x3f3f3f
using namespace std;
ifstream is ("energii.in");
ofstream os ("energii.out");
int e[1001], c[1001], sol[100001];
int n, w, wmax;
void Read();
int main()
{
    Read();
    for(int i = 1; i <= w; ++i)
        sol[i] = INF;
    for(int i = 1; i <= n; ++i)
        for(int j = w; j >= 1; --j)
        {
            if(e[i]>j)
                sol[j]=min(c[i],sol[j]);
            else
                sol[j]=min(sol[j-e[i]]+c[i],sol[j]);
        }
    if(sol[w] == INF)
        os << -1;
    else
        os << sol[w];
}

void Read()
{
    is >> n >> w;
    for(int i = 1; i <= n; ++i)
        is >> e[i] >> c[i];
}