#include <iostream>
#include <stdio.h>
using namespace std;
FILE *in,*out;
int g,w,i,j;
int cost[1002],e[1002],minim[5002];
int main()
{
    in=fopen("energii.in","r");
    out=fopen("energii.out","w");
    fscanf(in,"%d %d",&g,&w);
    for(i=0; i<g; i++)
        fscanf(in,"%d%d",&e[i],&cost[i]);
    for(i=1; i<=w; i++)
        minim[i]=-1;
    for(i=0; i<g; i++)
    {
        for(j=w-1; j>=0; j--)
        {
            if(minim[j]!=-1)
            {

                if(j+e[i]>=w)
                {
                    if(minim[j]+cost[i]<minim[w] && minim[w]!=-1)
                        minim[w]=minim[j]+cost[i];
                    else if(minim[w]==-1)
                        minim[w]=minim[j]+cost[i];
                }
                else
                {
                    if(minim[j]+cost[i]<minim[j+e[i]] && minim[j+e[i]]!=-1)
                        minim[j+e[i]]=minim[j]+cost[i];
                    else if(minim[j+e[i]]==-1)
                        minim[j+e[i]]=minim[j]+cost[i];

                }
            }
        }
    }

        fprintf(out,"%d",minim[w]);
        return 0;
    }