#include <bits/stdc++.h>

using namespace std;

ifstream f("energii.in");
ofstream g("energii.out");

const int INF=1e9;
int gen,w;

int main()
{
    f>>gen>>w;
    int en[gen+5],ct[gen+5];
    for (int i=1;i<=gen;i++)
        f>>en[i]>>ct[i];

    int dp[gen+5][w+5];
    for (int i=0;i<=w;i++)
        dp[0][i]=INF;

    for (int i=1;i<=gen;i++)
        for (int j=0;j<=w;j++)
            if (j<=en[i])
                dp[i][j]=min(dp[i-1][j],ct[i]);
            else
                dp[i][j]=min(dp[i-1][j],dp[i-1][j-en[i]]+ct[i]);

    if (!(dp[gen][w]<INF))
        g<<-1;
    else
        g<<dp[gen][w];
    return 0;
}