#include <bits/stdc++.h>
#define cin ci
#define cout co
#define int long long
using namespace std;
ifstream cin("energii.in");
ofstream cout("energii.out");
const int inf = 1e18;
const int Wmax = 1e4 + 5;
int n, w;
vector<int> dp;
vector<pair<int, int>> v;
int32_t main()
{
    cin >> n >> w;
    dp.assign(Wmax + 5, inf);
    v.resize(n + 5);
    for(int i = 1; i <= n; i ++)
        cin >> v[i].first >> v[i].second;

    dp[0] = 0;
    for(int i = 1; i <= n; i ++)
        for(int j = Wmax; j >= v[i].first; j --)
            if(dp[j - v[i].first] + v[i].second < dp[j])
                dp[j] = dp[j - v[i].first] + v[i].second;

    int ans = inf;
    for(int j = w; j <= Wmax; j ++)
        ans = min(ans, dp[j]);
    if(ans == inf)
        cout << "-1";
    else
        cout << ans;

    return 0;
}