#include <iostream>
#include <fstream>
#include <algorithm>
using namespace std;
ifstream f ("energii.in");
ofstream g ("energii.out");
int n,e,s,i,cost;
struct generator
{
    int en,co;
}v[1004];
bool comp(generator a, generator b)
{
    if(a.en<b.en) return false;
    if(a.en==b.en and a.co>b.co) return false;
    return true;
}
int main()
{
    f >> n >> e;
    for(i=1; i<=n; i++) {
        f >> v[i].en >> v[i].co;
    }
    sort(v+1,v+n+1,comp);
    i=1;
    while(s<e and i<=n) {
        s+=v[i].en;
        cost+=v[i].co;
        i++;
    }
    if(s>=e) g << cost;
    else g << -1;
    return 0;
}