#include <bits/stdc++.h>
using namespace std;
int n,s,a,b,i,j,dp[10010],ans=INT_MAX;
int main()
{
    ifstream f ("energii.in");
    ofstream g ("energii.out");
    f>>n>>s;
    for(i=1;i<=2*s;++i)dp[i]=10000010;
    for(i=1; i<=n; ++i)
    {
        f>>a>>b;
        for(j=s*2; j>=a; --j)
            dp[j]=min(dp[j],dp[j-a]+b);
    }
    for(i=s; i<=s*2; ++i)
        if(dp[i]!=10000010)
        {
            ans=min(ans,dp[i]);
        }
    if(ans==INT_MAX)g<<-1;
    else g<<ans;
    return 0;
}