#include <bits/stdc++.h>
#define int long long
using namespace std;

const int nm=15005;

int dp[nm];

struct Cows
{
    int x, y;
}v[1005];

signed main()
{
    ifstream cin("energii.in");
    ofstream cout("energii.out");
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
    cout.tie(nullptr);
    int n, w, minn=1e9;
    cin>>n>>w;
    for(int i=1; i<=n; i++)
    {
        cin>>v[i].x>>v[i].y;
    }
    for(int i=0; i<nm; i++)
        dp[i]=1e9;
    dp[0]=0;
    for(int i=1; i<=n; i++)
    {
        for(int j=nm-1; j>=0; j--)
        {
            if(dp[j-v[i].x]!=1e9)
                dp[j]=min(dp[j], dp[j-v[i].x]+v[i].y);

            if(j>=w)
                minn=min(minn, dp[j]);
        }
    }
    if(minn==1e9)
        cout<<-1;
    else
        cout<<minn;
    return 0;
}