#include <bits/stdc++.h>

using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");
const int Nmax = 1000 + 5;
const int Dmax = 10001 + 5001 + 5;
int n, pg, p, c, ans;
int dp[Dmax];
int main()
{
    fin >> n >> pg;
    dp[0] = 0; ans = 1 << 30;
    for(int i = 1; i <= pg + 10002; ++i)
        dp[i] = 1 << 30;
    for(int i = 1; i <= n; ++i)
    {
        fin >> p >> c;
        for(int j = pg - 1; j >= 0; --j)
            if(dp[j] != 1 << 30)
            {
                dp[j + p] = min(dp[j + p], dp[j] + c);
                if(j + p >= pg)
                    ans = min(dp[j + p], ans);
            }
        dp[p] = min(dp[p], c);
        if(p >= pg)
            ans = min(dp[p], ans);
    }
    if(ans == 1 << 30)ans = -1;
    fout << ans;
    return 0;
}