#include <fstream>

using namespace std;

ifstream fin("energii.in");
ofstream fout("energii.out");

int n, wtMax, w[1003], v[1003], dp[5003];

int main() {
    fin >> n >> wtMax;
    for(int i = 1; i <= n; i++) {
        fin >> w[i] >> v[i];
    }
    fin.close();
    for(int i = 1; i <= wtMax; i++) {
        dp[i] = (int) 2e9 + 5;
    }
    dp[1] = 0;
    int wt = 2e9 + 5;
    for(int i = 1; i <= n; i++) {
        for(int j = wtMax - 1; j >= 0; j--) {
            if(dp[j] != 2e9 + 5) {
                if(j + w[i] >= wtMax) {
                    wt = min(wt, v[i] + dp[j]);
                } else {
                    dp[j + w[i]] = min(dp[j + w[i]], v[i] + dp[j]);
                }
            }
        }
    }
    fout << (wt != 2e9 + 5 ? wt : -1);
    return 0;
}