#include <cstdio>
#include <cmath>
#include <iostream>
#include <algorithm>
#include <vector>
using namespace std;

#define rep(i, from, to) for (int i = from; i < (int)to; ++i)
#define trav(a, x) for (auto& a : x)
#define all(x) x.begin(), x.end()
#define sz(x) (int)x.size()
typedef long long ll; 
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef vector<int> vi;

const int N = 1111;
int g, w, ans;

struct gen {
    int cantitate;
    int cost;
} a[N];

bool compare1(gen a, gen b) {
    return a.cantitate > b.cantitate;
}

bool compare2(gen a, gen b) {
    return a.cost < b.cost;
}

int main() {
    freopen("energii.in", "r", stdin);
    freopen("energii.out", "w", stdout);
    cin >> g >> w;
    for (int i = 0; i < g; i++) {
        cin >> a[i].cantitate >> a[i].cost;
    }
    int p = 0;
    for (int i = 0; i < g; i++) {
        p += a[i].cantitate;
    }
    if (p < w) {
        cout << -1 << endl;;
        return 0;
    }
    sort(a, a + g, compare1);
    int k = 0, sum = 0;
    int cost = 0;
    while (k < g && sum < w) {
        sum += a[k].cantitate;
        cost += a[k].cost;
        k++;
    } 
    if (sum >= w) ans = max(ans, cost);
    cost = 0, sum = 0, k = 0;
    sort(a, a + g, compare2);
    while (k < g && sum < w) {
        sum += a[k].cantitate;
        cost += a[k].cost;
        k++;
    }
    if (sum >= w) ans = min(ans, cost);
    cout << ans << endl;
}