#include <iostream>
#include <cstdio>
#define inf 1000000
FILE *f,*g;
using namespace std;

int main()
{
    f=fopen("energii.in","r");
    g=fopen("energii.out","w");
    int G,W,E[10001],i,j,a,b;
    fscanf(f,"%d%d",&G,&W);
    for(i=1;i<=W;i++)
    {
        E[i]=inf;
    }
    for(i=1;i<=G;i++)
    {
        fscanf(f,"%d%d",&a,&b);
        for(j=W;j>=0;j--)
        {
            if(E[j]!=inf)
            {
                if(j+a<=W)
                {
                    if(E[j+a]>E[j]+b)
                    {
                        E[j+a]=E[j]+b;
                    }
                }
                else
                {
                    if(E[W]>E[j]+b)
                    {
                        E[W]=E[j]+b;
                    }
                }
            }
        }
    }
    if(E[W]==inf)
    {
        fprintf(g,"-1");
    }
    else
    {
        fprintf(g,"%d",E[W]);
    }
    fclose(f);
    fclose(g);
    return 0;
}