#include<fstream>
using namespace std;ifstream cin("energii.in");ofstream cout("energii.out");int G,W,a[10010],x,y;int main(){cin>>G>>W;for(int i=0;i<=W;i++)a[i]=100000;for(int i=0;i<G;i++){cin>>x>>y;if (x >= W&&a[W]>y)a[W] = y;for(int j=W;j>0;j--){if(j<x){a[j]=min(a[j],y);}else{a[j]=min(a[j-x]+y,a[j]);}}}if(a[W]==10000000)cout<<"-1";else cout<<a[W];}