#include <cstdio>
#include <cstring>
#define inf 1<<29
#define wmax 5002
#define gmax 1002
using namespace std;

int pow[wmax];
// in vectorul pow[i] retin costul minim pt a obtine o putere>=i; initializat initial cu inf
int n, w;

struct centrala
{

    int e, c;
} v[gmax];

void read()
{
    freopen("energii.in", "r", stdin);
    freopen("energii.out", "w", stdout);

    scanf("%i %i", &n, &w);
    for(int i=1; i<=n; i++)
        scanf("%i %i", &v[i].e, &v[i].c);
}


int main()
{
    read();
    for(int i=0; i<=w; i++)
        pow[i]=inf;
    //memset(pow, inf, 100);
    for(int i=1; i<=n; i++)
    {


        for(int j=v[i].e+1; j<=w; j++)
            if(pow[j-v[i].e]+v[i].c<pow[j])
                pow[j]=pow[j-v[i].e]+v[i].c;

        for(int j=1; j<=v[i].e; j++)
            if(v[i].c<pow[j])
                pow[j]=v[i].c;
    }
    if(pow[w]!=inf)
        printf("%i\n", pow[w]);
    else printf("-1\n");
    return 0;
}