#include <iostream>
#include <cstdio>
#define NMAX 1002
#define WMAX 10020
#define inf 0x3f3f3f3f
using namespace std;

int N,W;
int costuri[NMAX];
int puteri[NMAX];
int dp[WMAX];
int rez = inf;

void citire()
{
    scanf("%d%d",&N,&W);
    for(int i=1;i<=N;i++)
        scanf("%d%d",&puteri[i],&costuri[i]);
}

void rezolvare()
{
    for(int i=1;i<=WMAX;i++)
        dp[i] = inf;
    dp[0] = 0;

    for(int i=1;i<=N;i++)
        for(int j=WMAX-1;j>=puteri[i];j--)
            dp[j] = min(dp[j],dp[j-puteri[i]]+costuri[i]);

    for(int i=W;i<WMAX-1;i++)
        if(rez>dp[i])
            rez=dp[i];


    if(rez == inf)
        cout<<-1;
    else
        cout<<rez;
    cout<<"\n";
}

int main()
{
    freopen("energii.in","r",stdin);
    freopen("energii.out","w",stdout);
    citire();
    rezolvare();
    return 0;
}