#include <bits/stdc++.h>

#define VMAX 5010
#define NMAX 1010
#define LOG 19
#define INF (long long)(10e9)
#define MOD 1000000007
#define ll long long int


#define NIL 0
#define CMAX 1000000

using namespace std;
ifstream fin("energii.in");
ofstream fout("energii.out");


int dp[VMAX+2];
int cg[NMAX+1],eg[NMAX+1];
int w,n;

int main()
{
    fin >> n >> w;
    for(int i=1;i<=n;i++)
    {
        fin >> eg[i] >> cg[i];
    }
    for(int j=1;j<=w;j++)
    {
        dp[j]=INF;
    }
    for(int i=1;i<=n;i++)
    {
        for(int j=w-1;j>=0;j--)
        {
            if(dp[j]!=INF)
            {
                int k =j + eg[i];
                if(k > w)
                {
                    k=w;
                }
                dp[k] = min(dp[k],dp[j]+cg[i]);

            }
        }
    }
    if(dp[w]==INF)
    {
        fout << -1;
    }
    else
    {
        fout << dp[w];
    }
}