#include <bits/stdc++.h>

using namespace std;

ifstream fin("energii.in");
ofstream fout("energii.out");
int n, g, gr[1005], pr[1005], d[10005], r, i, s;

static inline int calc(int n, int g){
    for(int i = 1; i <= g; i++) d[i] = 999999999;
    for(int i = 1; i <= n; i++) {
        for(int j = g; j >= gr[i]; j--) d[j] = min(d[j], d[j - gr[i]] + pr[i]);
    }
    int r = 999999999;
    for(int j = g / 2; j <= g; j++)
        r = min(r, d[j]);
    return r;
}

int main() {
    fin >> n >> g;
    s = 0;
    for(i = 1; i <= n; i++){
        fin >> gr[i] >> pr[i];
        s += gr[i];
    }
    r = 999999999;
    if(s < g) fout << -1;
    else {
        r = min(r, calc(n, 2 * g));
        fout << r;
    }

    return 0;
}