// Example program
#include <bits/stdc++.h>
#define INF 0x3f3f3f3f
using namespace std;

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

vector <pair<int,int>> ene;
int dp[15005];

int main()
{
    int g, w;
    f>>g>>w;
    for(int i = 0, te, tc; i < g; i++)
    {
        f>>te>>tc;
        ene.push_back(make_pair(te, tc));
    }
    
    for(int i = 1; i < 15006; i++)
    {
        dp[i] = INF;
    }
    
    for(int i = 0; i < ene.size(); i++)
    {
        for(int j = w; j >= 0; j--)
        {
            if(dp[j] != INF)
            {
                dp[j + ene[i].first] = min(dp[j + ene[i].first], dp[j] + ene[i].second);
            }
        }
    }
    int answer = INF;
    for(int i = w; i < w + 10000; i++)
    {   
        if(dp[i] != INF)
        {
            answer = min(answer, dp[i]);
        }
    }
    if(answer != INF)
    g<<answer;
    else
    g<<-1;
}