#include <fstream>
using namespace std;
ifstream inputeaza("energii.in");
ofstream outputeaza("energii.out");
#define inf 255



int a[100000],i,j,c,p,g,w;

int main(){

    inputeaza >> g >> w;
    for (i=1; i<=w+10001; i++) a[i]=inf;

    for (i=1; i<=g; i++){
        inputeaza >> p >> c;
        for (j=w; j>=0; j--)
            if (a[j]+c<a[j+p]) a[j+p]=a[j]+c;
    }

    c=inf;
    for (i=w; i<=w+10001; i++) if (a[i]<c) c=a[i];

    if (c==inf) outputeaza << "-1"; else outputeaza << c;

    return 0;
}