#include <fstream>
#include <iostream>

using namespace std;

ifstream f("energii.in");
ofstream g("energii.out");

int v[5005];
int n,x,y,m;

int main(){

    f>>n>>m;
    for(int i=1; i<=m; i++)
        v[i] = 5000001;
    for(int i=1; i<=n; i++){
        f>>x>>y;
        for(int j=m; j>=0; j--){
            if(j+x < m)
                v[j+x] = min(v[j+x],v[j]+y);
            else
                v[m] = min(v[m],v[j]+y);
        }
    }
    if(v[m] != 5000001) g<<v[m];
    else g<<-1;
}