#include <bits/stdc++.h>

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