#include <bits/stdc++.h>
using namespace std;
ifstream fin ("energii.in");
ofstream fout("energii.out");
int n,g,dp[5010],e[1010],w[1010],best=INT_MAX,i,cw;
int main()
{
    fin>>n>>g;
    for(i=1;i<=n;i++)
        fin>>e[i]>>w[i];
    for(i=0;i<=g;i++)
        dp[i]=1000010;
    for(i=1;i<=n;i++)
        for(cw=g;cw>=0;cw--)
            if(cw<=e[i])
                dp[cw]=min(dp[cw],w[i]);
            else dp[cw]=min(dp[cw],dp[cw-e[i]]+w[i]);
    if(dp[g]==1000010)
        fout<<"-1\n";
    else fout<<dp[g]<<'\n';
    return 0;
}