#include <fstream>
#define lim 5000
#define INF 1e9

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

int dp[lim+5],n,W,p,g;

int main()
{
    in>>n>>W;
    for(int i=0; i<=W; i++) dp[i]=INF;

    for(int i=1; i<=n; i++)
    {
        in>>p>>g;
        for(int j=W-1; j>=1; j--)
        {
            if(p+j >= W)
            {
                if(g + dp[j] <= dp[W])
                    dp[W] = g+dp[j];
            }
            else if(g + dp[j] <= dp[j+p])
                dp[j+p] = dp[j] + g;
        }
        if(g < dp[p]) dp[p] = g;
    }

    if(dp[W] != INF) out<<dp[W];
    else out<<-1;
    return 0;
}