#include <bits/stdc++.h>

using namespace std;
ifstream in("energii.in");
ofstream out("energii.out");
int n,g,e[1100],c[1100],dp[5100],ans;
int main()
{
    in>>n>>g;
    for(int i=1;i<=n;i++) in>>e[i]>>c[i];
    ans=100000000;
    for(int i=1;i<=g;i++) dp[i]=100000000;
    for(int i=1;i<=n;i++)
    {
        for(int j=g;j>0&&j-e[i]>=0;j--)
            dp[j]=min(dp[j],dp[j-e[i]]+c[i]);
        ans=min(ans,dp[g]);
    }
    if(ans==100000000) out<<-1;
    else out<<ans;
    return 0;
}