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