#include <bits/stdc++.h>

#define VMAX 5000
#define NMAX 1000
#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];
    }
    int res=INF;
    for(int j=VMAX;j>=1;j--)
    {
        dp[j]=INF;
    }
    for(int i=1;i<=n;i++)
    {
        for(int j=VMAX;j>=0;j--)
        {
            if(j+eg[i] >= w)
            {
                res=min(res,dp[j]+cg[i]);
            }
            else
            {
                dp[j+eg[i]] = min(dp[j+eg[i]],dp[j]+cg[i]);
            }
        }
    }
    fout << (res==INF ? -1 : res);
}