#include <bits/stdc++.h>

using namespace std;

ifstream fin("energii.in");
ofstream fout("energii.out");
const int inf = 1e7;
int n, i, j, e[5002], pr[5002];
int fr[5002], boot;

int main() {
    fin >> n >> boot;
    for(i = 1; i <= n; i++) fin >> e[i] >> pr[i];

    for(i = 1; i <= boot; i++) fr[i] = inf;

    fr[0] = 0;
    for(i = 1; i <= n; i++) {
        for(j = boot; j >= 0; j--) {
            if(fr[j] != inf) {
                int ener = min(boot, j + e[i]);

                fr[ener] = min(fr[ener], fr[j] + pr[i]);
            }
        }
    }

    if(fr[boot] == inf) fout << "-1";
    else fout << fr[boot];

    return 0;
}