#include <iostream>
#include <cstdio>

using namespace std;

int n,G,w,p,x[10005];

int main()
{
    int i,j;
    FILE *f=fopen("energii.in","r");
    FILE *g=fopen("energii.out","w");
    fscanf(f,"%d%d",&n,&G);
    for(i=1;i<=n;i++)
    {
        fscanf(f,"%d%d",&w,&p);
        for(j=1;j<=w;j++)
        {
            if(x[j])
            {
                if(x[j+w])
                    x[j+w]=min(p+x[j],x[j+w]);
                else x[j+w]=p+x[j];
               // maxx=j+w;
                x[j]=min(p,x[j]);
            }
            else x[j]=p;
        }
    }
    if(x[G])
        fprintf(g,"%d\n",x[G]);
    else fprintf(g,"-1\n");
    return 0;
}